HIROKI SAITO
| Department of Engineering Science | Professor |
| Cluster III (Fundamental Science and Engineering) | Professor |
| Institute for Advanced Science | Professor |
- Profile:
-1999 量子光学：原子と光の相互作用による非古典的状態（スクイズド状態）に関する研究
2000- 量子凝縮体：超低温量子気体（ボース・アインシュタイン凝縮体）の諸物性
Researcher Information
Career
Research Activity Information
Paper
- Quantum droplets with magnetic vortices in spinor dipolar Bose-Einstein condensates
Shaoxiong Li; Hiroki Saito
Corresponding, Physical Review Research, American Physical Society (APS), 6, 4, L042049-1-L042049-10, 25 Nov. 2024, Peer-reviwed, Motivated by the recent experimental realization of a Bose-Einstein condensate (BEC) of europium atoms, we investigate the self-bound droplet state for a dipolar BEC with spin degrees of freedom. Under a sufficiently weak magnetic field, the droplet has a torus shape with circulating spin vectors, which is referred to as a magnetic vortex. The ground state transforms from a torus to a cigar shape through bistability with increasing magnetic field. Dynamical change of the magnetic field causes the torus to rotate due to the Einstein–de Haas effect. The magnetic vortices form a supersolid in a confined system.
Published by the American Physical Society 2024
Scientific journal - Long Lifetime Supersolid of Two Component Dipolar BEC: Dynamics of Supersolid Formation
Shaoxiong Li; Hiroki Saito
Corresponding, Proceedings of the 29th International Conference on Low Temperature Physics (LT29), Journal of the Physical Society of Japan, 22 May 2023, Peer-reviwed
International conference proceedings - Phase separation and multistability of a two-component Bose-Einstein condensate in an optical cavity
Abid Ali; Farhan Saif; Hiroki Saito
Corresponding, Physical Review A, 105, 063318/1-063318/9, 17 Jun. 2022, Peer-reviwed
Scientific journal, English - Long-lifetime supersolid in a two-component dipolar Bose-Einstein condensate
Shaoxiong Li; Uyen Ngoc Le; Hiroki Saito
Corresponding, Physical Review A, 105, L061302/1-L061302/7, 13 Jun. 2022, Peer-reviwed
Scientific journal, English - Spin-orbit-coupled Bose gases with nonlocal Rydberg interactions held under a toroidal trap
Xiao-Fei Zhang; Lin Wen; Lin-Xue Wang; G.-P. Chen; R.-B. Tan; Hiroki Saito
Physical Review A, 105, 033306/1-033306/9, 14 Mar. 2022, Peer-reviwed
Scientific journal, English - Hydrodynamic generation of skyrmions in a two-component Bose-Einstein condensate
Kyoshiro Sakaguchi; Keisuke Jimbo; Hiroki Saito
Corresponding, Physical Review A, 105, 013312/1-013312/7, 14 Jan. 2022, Peer-reviwed
Scientific journal, English - Surfactant behavior in three-component Bose-Einstein condensates
Keisuke Jimbo; Hiroki Saito
Corresponding, Physical Review A, 103, 063323/1-063323/10, 28 Jun. 2021, Peer-reviwed
Scientific journal, English - Human-Machine Collaboration in Quantum Many-Body Problems
Hiroki Saito
Journal of the Physical Society of Japan, 17, 06/1-06/2, 30 Jun. 2020, Invited
Scientific journal, English - Creation and Manipulation of Quantized Vortices in Bose–Einstein Condensates Using Reinforcement Learning
Hiroki Saito
Journal of the Physical Society of Japan, 89, 074006/1-074006/8, 24 Jun. 2020, Peer-reviwed
Scientific journal, English - Effects of atom numbers on the miscibility-immiscibility transition of a binary Bose-Einstein condensate
Lin Wen; Hui Guo; Ya-Jun Wang; Ai-Yuan Hu; Hiroki Saito; Chao-Qing Dai; Xiao-Fei Zhang
Physical Review A, 101, 033610/1-033610/9, 13 Mar. 2020, Peer-reviwed
Scientific journal, English - Neural-network quantum states at finite temperature
Naoki Irikura; Hiroki Saito
Corresponding, Physical Review Research, 2, 013284/1-013284/6, 09 Mar. 2020, Peer-reviwed
Scientific journal, English - Faraday patterns generated by Rabi oscillation in a binary Bose-Einstein condensate
Terun Chen; Kosuke Shibata; Yujiro Eto; Takuya Hirano; Hiroki Saito
Corresponding, Physical Review A, American Physical Society (APS), 100, 6, 063610/1-063610/7, 05 Dec. 2019, Peer-reviwed
Scientific journal, English - Symmetry-breaking instability of leapfrogging vortex rings in a Bose-Einstein condensate
Mayumi Ikuta; Yumi Sugano; Hiroki Saito
Corresponding, Physical Review A, 99, 043610/1-043610/8, 09 Apr. 2019, Peer-reviwed
Scientific journal, English - Orthogonal and antiparallel vortex tubes and energy cascades in quantum turbulence
Tsuyoshi Kadokura; Hiroki Saito
Corresponding, Physical Review Fluids, 3, 104606/1-104606/12, 17 Oct. 2018, Peer-reviwed
Scientific journal, English - Stationary states and rotational properties of spin–orbit-coupled Bose–Einstein condensates held under a toroidal trap
Zhang-Ming He; Xiao-Fei Zhang; Masaya Kato; Wei Han; Hiroki Saito
Physics Letters, Section A: General, Atomic and Solid State Physics, Elsevier B.V., 382, 25, 1690-1694, 26 Jun. 2018, Peer-reviwed, We consider a pseudospin-1/2 Bose–Einstein condensate with Rashba spin–orbit coupling in a two-dimensional toroidal trap. By solving the damped Gross–Pitaevskii equations for this system, we show that the system exhibits a rich variety of stationary states, such as vehicle wheel and flower-petal stripe patterns. These stationary states are stable against perturbation with thermal energy and can survive for a long time. In the presence of rotation, our results show that the rotating systems have exotic vortex configurations. These phenomenon originates from the interplay among spin–orbit coupling, trap geometry, and rotation.
Scientific journal, English - Dynamics of vortices followed by the collapse of ring dark solitons in a two-component Bose-Einstein condensate
Lin-Xue Wang; Chao-Qing Dai; Lin Wen; Tao Liu; Hai-Feng Jiang; Hiroki Saito; Shou-Gang Zhang; Xiao-Fei Zhang
Physical Review A, American Physical Society, 97, 6, 063607/1-063607/7, 11 Jun. 2018, Peer-reviwed, We explore the effects of system parameters on the dynamics of ring dark solitons (RDSs) and vortices followed by the collapse of RDSs in a two-component Bose-Einstein condensate (BEC). The system exhibits complicated dynamical behaviors, which are quite different from those in a scalar BEC. For two shallow RDSs with equal initial depths, the dynamical trajectories of generated vortex dipoles are similar to those in a scalar BEC, but the time for vortex dipoles to perform a periodic motion is increased. In particular, there exists a critical depth, above which vortex dipoles first move along the vertical direction and then preform complicated dynamics, including their rearrangement and recombination. Finally, we consider the case of unequal initial depths and find that the number of created vortices is determined by the depth of the shallow RDS, while their initial moving direction is determined by the deeper one.
Scientific journal, English - Fingering instabilities and pattern formation in a two-component dipolar Bose-Einstein condensate
Kui-Tian Xi; Tim Byrnes; Hiroki Saito
Physical Review A, American Physical Society, 97, 2, 023625/1-023625/9, 16 Feb. 2018, Peer-reviwed, We study fingering instabilities and pattern formation at the interface of an oppositely polarized two-component Bose-Einstein condensate with strong dipole-dipole interactions in three dimensions. It is shown that the rotational symmetry is spontaneously broken by fingering instability when the dipole-dipole interactions are strengthened. Frog-shaped and mushroom-shaped patterns emerge during the dynamics due to the dipolar interactions. We also demonstrate the spontaneous density modulation and domain growth of a two-component dipolar BEC in the dynamics. Bogoliubov analyses in the two-dimensional approximation are performed, and the characteristic lengths of the domains are estimated analytically. Patterns resembling those in magnetic classical fluids are modulated when the number ratio of atoms, the trap ratio of the external potential, or tilted polarization with respect to the z direction is varied.
Scientific journal, English - Spinor dynamics in a mixture of spin-1 and spin-2 Bose-Einstein condensates
Yujiro Eto; Hitoshi Shibayama; Hiroki Saito; Takuya Hirano
Physical Review A, American Physical Society, 97, 2, 021602/1-021602/5, 13 Feb. 2018, Peer-reviwed, The spinor dynamics of Bose-Einstein condensates of Rb87 atoms with hyperfine spins of 1 and 2 are investigated. A mixture of spinor condensates is generated in the transversely polarized spin-1 and the longitudinally polarized spin-2 states using simultaneous Ramsey interferometry. In the subsequent dynamics, temporal modulation of spin-1 magnetization is observed in the spinor mixture due to the spin-dependent interaction with the spin-2 component. By comparison with numerical simulations based on the Gross-Pitaevskii equation, we find that the observed nonferromagnetic dynamics reflect the ground-state properties of the spinor mixture.
Scientific journal, English - Ground-state phases of a mixture of spin-1 and spin-2 Bose-Einstein condensates
Naoki Irikura; Yujiro Eto; Takuya Hirano; Hiroki Saito
Physical Review A, American Physical Society, 97, 2, 023622/1-023622/10, 13 Feb. 2018, Peer-reviwed, We investigate the ground-state phases of a mixture of spin-1 and spin-2 Bose-Einstein condensates at zero magnetic field. In addition to the intraspin interactions, two spin-dependent interaction coefficients are introduced to describe the interspin interaction. We systematically explore the wide parameter space, and obtain phase diagrams containing a rich variety of phases. For example, there exists a phase in which the spin-1 and spin-2 vectors are tilted relative to each other breaking the axial symmetry.
Scientific journal, English - Machine learning technique to find quantum many-body ground states of bosons on a lattice
Hiroki Saito; Masaya Kato
Journal of the Physical Society of Japan, Physical Society of Japan, 87, 1, 014001/1-014001/8, 2018, Peer-reviwed, We have developed a variational method to obtain many-body ground states of the Bose-Hubbard model using feedforward artificial neural networks. A fully connected network with a single hidden layer works better than a fully connected network with multiple hidden layers, and a multilayer convolutional network is more efficient than a fully connected network. AdaGrad and Adam are optimization methods that work well. Moreover, we show that many-body ground states with different numbers of particles can be generated by a single network.
Scientific journal, English - Method to solve quantum few-body problems with artificial neural networks
Hiroki Saito
Journal of the Physical Society of Japan, Physical Society of Japan, 87, 7, 074002/1-074002/6, 2018, Peer-reviwed, A machine learning technique to obtain the ground states of quantum few-body systems using artificial neural networks is developed. Bosons in continuous space are considered and a neural network is optimized in such a way that when particle positions are input into the network, the ground-state wave function is output from the network. The method is applied to the Calogero–Sutherland model in one-dimensional space and Efimov bound states in three-dimensional space.
Scientific journal, English - Moving obstacle potential in a spin-orbit-coupled Bose-Einstein condensate
Masaya Kato; Xiao-Fei Zhang; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 96, 3, 033613/1-033613/8, Sep. 2017, Peer-reviwed, We investigate the dynamics around an obstacle potential moving in the plane-wave state of a pseudospin-1/2 Bose-Einstein condensate with Rashba spin-orbit coupling. We numerically investigate the dynamics of the system and find that it depends not only on the velocity of the obstacle but also significantly on the direction of obstacle motion, both of which are verified by the Bogoliubov analysis. The excitation diagram with respect to the velocity and direction is obtained. The dependence of the critical velocity on the strength of the spin-orbit coupling and the size of the obstacle is also investigated.
Scientific journal, English - Solving the Bose-Hubbard model with machine learning
Hiroki Saito
Journal of the Physical Society of Japan, The Physical Society of Japan, 86, 9, 093001/1-093001/4, 31 Jul. 2017, Peer-reviwed
Scientific journal, English - Vortex pairs in a spin-orbit-coupled Bose-Einstein condensate
Masaya Kato; Xiao-Fei Zhang; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 95, 4, 043605/1-7, Apr. 2017, Peer-reviwed, Static and dynamic properties of vortices in a two-component Bose-Einstein condensate with Rashba spin-orbit coupling are investigated. The mass current around a vortex core in the plane-wave phase is found to be deformed by the spin-orbit coupling, and this makes the dynamics of the vortex pairs quite different from those in a scalar Bose-Einstein condensate. The velocity of a vortex-antivortex pair is much smaller than that without spin-orbit coupling, and there exist stationary states. Two vortices with the same circulation move away from each other or unite to form a stationary state.
Scientific journal, English - Spin-orbit-coupled Bose-Einstein condensates held under a toroidal trap
Xiao-Fei Zhang; Masaya Kato; Wei Han; Shou-Gang Zhang; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 95, 3, 033620 1-7, Mar. 2017, Peer-reviwed, We study a quasispin-1/2 Bose-Einstein condensate with synthetically generated spin-orbit coupling in a toroidal trap and show that the system has a rich variety of ground states. As the central hole region increases, i.e., the potential changes from harmoniclike to ringlike, the condensate exhibits a variety of structures, such as a modified stripe, an alternately arranged stripe, and countercircling states. In the limit of a quasi-one-dimensional ring, the quantum many-body ground state is obtained, which is found to be the fragmented condensate.
Scientific journal, English - Topological defect formation in rotating binary dipolar Bose-Einstein condensate
Xiao-Fei Zhang; Wei Han; Hai-Feng Jiang; Wu-Ming Liu; Hiroki Saito; Shou-Gang Zhang
Annals of Physics, 375, 368-377, Nov. 2016, Peer-reviwed
Scientific journal, English - Twisted spin vortices in a spin-1 Bose-Einstein condensate with Rashba spin-orbit coupling and dipole-dipole interaction
Masaya Kato; Xiao-Fei Zhang; Daichi Sasaki; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 94, 4, Oct. 2016, Peer-reviwed, We consider a spin-1 Bose-Einstein condensate with Rashba spin-orbit coupling and dipole-dipole interaction confined in a cigar-shaped trap. Due to the combined effects of spin-orbit coupling, dipole-dipole interaction, and trap geometry, the system exhibits a rich variety of ground-state spin structures, including twisted spin vortices. The ground-state phase diagram is determined with respect to the strengths of the spin-orbit coupling and dipole-dipole interaction.
Scientific journal, English - Self-rotation and synchronization in exciton-polariton condensates
Hiroki Saito; Rina Kanamoto
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 94, 16, 165306-1-165306-6, Oct. 2016, Peer-reviwed, Self-rotation occurs in an exciton-polariton condensate in a two-dimensional semiconductor microcavity pumped by a nonresonant Gaussian laser beam. A wave packet of the condensate spontaneously rotates around the center of the pumped region at a constant frequency breaking the rotation symmetry of the system. When two self-rotating condensates are created with an appropriate distance, synchronization occurs between the dynamics of the self-rotating condensates.
Scientific journal, English - Twisted spin vortices in a spinor-dipolar Bose-Einstein condensate with Rashba spin-orbit coupling
Masaya Kato; Xiao-Fei Zhang; Daichi Sasaki; Hiroki Saito
Physical Review A, 94, 043633-1-043633-6, Oct. 2016, Peer-reviwed
Scientific journal, English - Double-quantum spin vortices in SU(3) spin-orbit-coupled Bose gases
Wei Han; Xiao-Fei Zhang; Shu-Wei Song; Hiroki Saito; Wei Zhang; Wu-Ming Liu; Shou-Gang Zhang
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 94, 3, 033611-1-033611-9, Sep. 2016, Peer-reviwed, We show that double-quantum spin vortices, which are characterized by doubly quantized circulating spin currents and unmagnetized filled cores, can exist in the ground states of SU(3) spin-orbit-coupled Bose gases. It is found that the SU(3) spin-orbit coupling and spin-exchange interaction play important roles in determining the ground-state phase diagram. In the case of effective ferromagnetic spin interaction, the SU(3) spin-orbit coupling induces a threefold degeneracy to the magnetized ground state, while in the antiferromagnetic spin interaction case, the SU(3) spin-orbit coupling breaks the ordinary phase rule of spinor Bose gases and allows the spontaneous emergence of double-quantum spin vortices. This exotic topological defect is in stark contrast to the singly quantized spin vortices observed in existing experiments and can be readily observed by the current magnetization-sensitive phase-contrast imaging technique.
Scientific journal, English - Nonequilibrium dynamics induced by miscible-immiscible transition in binary Bose-Einstein condensates
Yujiro Eto; Masahiro Takahashi; Masaya Kunimi; Hiroki Saito; Takuya Hirano
NEW JOURNAL OF PHYSICS, IOP PUBLISHING LTD, 18, 073029-1-073029-6, Jul. 2016, Peer-reviwed, We have observed and characterized the nonequilibrium spatial dynamics of a two-component Rb-87 Bose-Einstein condensate (BEC) that is controllable switched back and forth between the miscible and immiscible phases of the phase separation transition by changing the internal states of the Rb-87 atoms. The subsequent evolution exhibits large scale oscillations of the spatial structure that involve component mixing and separation. We show that the larger total energy of the miscible system results in a higher oscillation frequency. This investigation introduces a new technique to control the miscibility and the spatial degrees of freedom in atomic BECs.
Scientific journal, English - Collision dynamics of skyrmions in a two-component Bose-Einstein condensate
Tomoya Kaneda; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 93, 3, 033611-1-033611-6, Mar. 2016, Peer-reviwed, The dynamics of skyrmions in a two-component Bose-Einstein condensate is numerically investigated in the mean-field theory. When two skyrmions collide with each other, they are first united and then scattered into various states. For head-on collisions, skyrmions with unit winding number are scattered. The collision dynamics with an impact parameter are shown to depend on the relative phase. These dynamic processes are characterized by integer winding numbers.
Scientific journal, English - Bouncing motion and penetration dynamics in multicomponent Bose-Einstein condensates
Yujiro Eto; Masahiro Takahashi; Keita Nabeta; Ryotaro Okada; Masaya Kunimi; Hiroki Saito; Takuya Hirano
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 93, 3, 033615/1-033615/6, Mar. 2016, Peer-reviwed, We investigate the dynamic properties of bouncing and penetration in colliding binary and ternaryBose-Einstein condensates comprised of different Zeeman or hyperfine states of Rb-87. Through the application ofmagnetic field gradient pulses, two-or three-component condensates in an optical trap are spatially separated and then made to collide. The subsequent evolutions are classified into two categories: repeated bouncing motion and mutual penetration after damped bounces. We experimentally observed mutual penetration for immiscible condensates, bouncing between miscible condensates, and domain formation for miscible condensates. From numerical simulations of the Gross-Pitaevskii equation, we find that the penetration time can be tuned by slightly changing the atomic interaction strengths.
Scientific journal, English - Droplet formation in a Bose-Einstein condensate with strong dipole-dipole interaction
Kui-Tian Xi; Hiroki Saito
Physical Review A, American Physical Society, 93, 1, 15 Jan. 2016, Peer-reviwed, Motivated by the recent experiment [H. Kadau, arXiv:1508.05007], we study roton instability and droplet formation in a Bose-Einstein condensate of Dy164 atoms with strong magnetic dipole-dipole interaction. We numerically solve the cubic-quintic Gross-Pitaevskii equation with dipole-dipole interaction, and show that the three-body interaction plays a significant role in the formation of droplet patterns. We numerically demonstrate the formation of droplet patterns and crystalline structures, decay of droplets, and hysteresis behavior, which are in good agreement with the experiment. Our numerical simulations provide the first prediction on the values of the three-body interaction in a Dy164 Bose-Einstein condensate. We also predict that the droplets remain stable during the time-of-flight expansion. From our results, further experiments investigating the three-body interaction in dipolar quantum gases are required.
Scientific journal, English - Droplet formation in a Bose-Einstein condensate with strong dipole-dipole interaction
Kui-Tian Xi; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 93, 1, 011604, Jan. 2016, Peer-reviwed, Motivated by the recent experiment [H. Kadau et al., arXiv: 1508.05007], we study roton instability and droplet formation in a Bose-Einstein condensate of Dy-164 atoms with strong magnetic dipole-dipole interaction. We numerically solve the cubic-quintic Gross-Pitaevskii equation with dipole-dipole interaction, and show that the three-body interaction plays a significant role in the formation of droplet patterns. We numerically demonstrate the formation of droplet patterns and crystalline structures, decay of droplets, and hysteresis behavior, which are in good agreement with the experiment. Our numerical simulations provide the first prediction on the values of the three-body interaction in a 164Dy Bose-Einstein condensate. We also predict that the droplets remain stable during the time-of-flight expansion. From our results, further experiments investigating the three-body interaction in dipolar quantum gases are required.
Scientific journal, English - Path-integral monte carlo study on a droplet of a dipolar bose-Einstein condensate stabilized by quantum fluctuation
Hiroki Saito
Journal of the Physical Society of Japan, Physical Society of Japan, 85, 5, 053001/1-4, 2016, Peer-reviwed, Motivated by recent experiments [H. Kadau et al., Nature (London) 530, 194 (2016)
I. Ferrier-Barbut et al., arXiv:1601.03318] and theoretical prediction (F. Wächtler and L. Santos, arXiv:1601.04501), the ground state of a dysprosium Bose-Einstein condensate with strong dipole-dipole interaction is studied by the path-integral Monte Carlo method. It is shown that quantum fluctuation can stabilize the condensate against dipolar collapse.
Scientific journal, English - Can we swim in superfluids?: Numerical demonstration of self-propulsion in a Bose-Einstein condensate
Hiroki Saito
Journal of the Physical Society of Japan, The Physical Society of Japan, 84, 11, 114001-1-114001-6, Oct. 2015, Peer-reviwed, We numerically investigated whether a deformable object can propel itself in a superfluid. Articulated bodies and multicomponent condensates are examined as swimmers. An articulated two-body swimmer cannot obtain locomotion without emitting excitations. More flexible swimmers can do so without the need to excite waves.
Scientific journal, English - Suppression of relative flow by multiple domains in two-component Bose-Einstein condensates
Yujiro Eto; Masaya Kunimi; Hidekatsu Tokita; Hiroki Saito; Takuya Hirano
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 92, 1, 013611-1-013611-5, Jul. 2015, Peer-reviwed, We investigate flow properties of immiscible Bose-Einstein condensates composed of two different Zeeman spin states of Rb-87. Two spatially overlapping condensates in the optical trap are prepared by application of a resonant radio-frequency pulse, and then the magnetic field gradient is applied in order to produce the atomic flow. We find that the spontaneous multiple-domain formation arising from the immiscible nature drastically changes the fluidity. The homogeneously overlapping condensates readily separate under the magnetic field gradient, and they form a stable configuration composed of the two layers. In contrast, the relative flow between two condensates is largely suppressed in the case where the magnetic field gradient is applied after spontaneous domain formation.
Scientific journal, English - Energy shift of magnons in a ferromagnetic spinor-dipolar Bose-Einstein condensate
Hiroki Saito; Masaya Kunimi
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 91, 4, 041603(R)-1-041603(R)-4, Apr. 2015, Peer-reviwed, Motivated by the recent experiment performed by the Berkeley group [G. E. Marti et al., Phys. Rev. Lett. 113, 165301 (2014)], we consider the dynamics of magnons in a spin-1 spinor-dipolar Bose-Einstein condensate, using mean-field theory. We show that the effective mass of a magnon is increased by the magnetic dipole-dipole interaction, as observed in the experiment. The magnon mass is also decreased by changing the direction of the magnetic field. The increase and decrease in the magnon mass manifest themselves in the acceleration of the magnons.
Scientific journal, English - Upper bound of one-magnon excitation and lower bound of effective mass for ferromagnetic spinor Bose and Fermi gases
Masaya Kunimi; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 91, 4, 043624-1-043624-6, Apr. 2015, Peer-reviwed, Using a variational method, we derive an exact upper bound for one-magnon excitation energy in ferromagnetic spinor gases, which limits the quantum corrections to the effective mass of a magnon to be positive. We also derive an upper bound for one-magnon excitation energy in lattice systems. The results hold for both Bose and Fermi systems in d dimensions as long as the interaction is local and invariant under spin rotation.
Scientific journal, English - Dynamics of a vortex dipole across a magnetic phase boundary in a spinor Bose-Einstein condensate
Tomoya Kaneda; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 90, 5, 053632-1-053632-7, Nov. 2014, Peer-reviwed, The dynamics of a vortex dipole in a spin-1 Bose-Einstein condensate in which magnetic phases are spatially distributed is investigated. When a vortex dipole travels from the ferromagnetic phase to the polar phase, or vice versa, it penetrates the phase boundary and transforms into one of the various spin vortex dipoles, such as a leapfrogging ferromagnetic-core vortex dipole and a half-quantum vortex dipole. Topological connections of spin wave functions across the phase boundary are discussed.
Scientific journal, English - Hysteresis in quantized vortex shedding
Tsuyoshi Kadokura; Jun Yoshida; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 90, 1, 013612-1-013612-5, Jul. 2014, Peer-reviwed, It is shown using numerical simulations that flow patterns around an obstacle potential moving in a superfluid exhibit hysteresis. In a certain velocity region, there is a bistability between stationary laminar flow and periodic vortex shedding. The bistability exists in two- and three-dimensional systems.
Scientific journal, English - Control of spin current in a Bose gas by periodic application of pi pulses
Yujiro Eto; Mark Sadgrove; Sho Hasegawa; Hiroki Saito; Takuya Hirano
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 90, 1, 013626, Jul. 2014, Peer-reviwed, We generate spin currents in an Rb-87 spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of two-body collisions. In addition, the spin coherence, as measured by the fringe contrast using Ramsey interferometry, is reduced drastically but experiences a weak revival due to in-trap oscillations. The spin current can be controlled using periodic p pulses (bang-bang control), producing longer spin-coherence times. Our results show that spin coherence can be maintained even in the presence of spin currents, with applications to quantum sensing in noisy environments.
Scientific journal, English - Comment on "Ground-state fragmentation phase transition for attractive bosons in anisotropic traps"
Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 89, 6, 067601-1-067601-2, Jun. 2014, Peer-reviwed, In a recent article [Phys. Rev. A 88, 063641 ( 2013)], Cizek and Kasevich claimed that quantum fragmentation occurs in themetastable state of a Bose-Einstein condensate with an attractive interaction confined in an elongated harmonic potential. This result was obtained using the two-state Gaussian variational method. However, modified methods show that no fragmentation occurs for the parameters used by Cizek and Kasevich.
Scientific journal, English - Observation of Dipole-Induced Spin Texture in an Rb-87 Bose-Einstein Condensate
Yujiro Eto; Hiroki Saito; Takuya Hirano
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 112, 18, 185301, May 2014, Peer-reviwed, We report the formation of spin texture resulting from the magnetic dipole-dipole interaction in a spin-2 Rb-87 Bose-Einstein condensate. The spinor condensate is prepared in the transversely polarized spin state and the time evolution is observed under a magnetic field of 90 mG with a gradient of 3 mG/cm using Stern-Gerlach imaging. The experimental results are compared with numerical simulations of the Gross-Pitaevskii equation, which reveals that the observed spatial modulation of the longitudinal magnetization is due to the spin precession in an effective magnetic field produced by the dipole-dipole interaction. These results show that the dipole-dipole interaction has considerable effects even on spinor condensates of alkali metal atoms.
Scientific journal, English - Many-body dynamics of a Bose-Einstein condensate collapsing by quantum tunneling
Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 89, 2, 023610, Feb. 2014, Peer-reviwed, The dynamics of a Bose-Einstein condensate of atoms having attractive interactions is studied using quantum many-body simulations. The collapse of the condensate by quantum tunneling is numerically demonstrated, and the tunneling rate is calculated. The correlation properties of the quantum many-body state are investigated.
Scientific journal, English - Kibble-Zurek mechanism in a trapped ferromagnetic Bose-Einstein condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
J. Phys.: Condens. Matter 25, 404212 (2013), 25, 404212, Sep. 2013, Peer-reviwed
Scientific journal, English - Dissipative structures of quantized vortices in a coherently pumped polariton superfluid
Tomohiko Aioi; Tsuyoshi Kadokura; Hiroki Saito
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 87, 20, 205312, May 2013, Peer-reviwed, Steady states reached in a coherently pumped exciton-polariton superfluid are investigated. As the pump parameter is changed, the translational symmetry of the uniform system is spontaneously broken, and various steady patterns of quantized vortices are formed. This is peculiar to nonequilibrium dissipative systems with continuous pumping.
Scientific journal, English - Control and detection of the Larmor precession of F=2 87Rb Bose-Einstein condensates by Ramsey interferometry and spin echo
Yujiro Eto; Sawako Sekine; Sho Hasegawa; Mark Sadgrove; Hiroki Saito; Takuya Hirano
Applied Physics Express, 6, Apr. 2013, Peer-reviwed
Scientific journal, English - Order-Disorder Oscillations in Exciton-Polariton Superfluids
Hiroki Saito; Tomohiko Aioi; Tsuyoshi Kadokura
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 110, 2, 026401, Jan. 2013, Peer-reviwed, The dynamics of an exciton-polariton superfluid resonantly pumped in a semiconductor microcavity are investigated by mean-field theory. Modulational instability develops into crystalline order, and then, ordered and disordered states alternately form. It is found that the crystalline order at rest can coexist with superflow. DOI: 10.1103/PhysRevLett.110.026401
Scientific journal, English - Modulation of a quantized vortex street with a vibrating obstacle
Hiroki Saito; Kenta Tazaki; Tomohiko Aioi
Procedia IUTAM, 9, 121-128, 2013, Peer-reviwed, Dynamics of a superfluid flow past an obstacle are investigated by solving the Gross-Pitaevskii equation numerically. For appropriate velocity and size of the obstacle, quantized vortices are periodically generated in the wake, which form a Bénard-von Kármán vortex street. It is found that vibration of an obstacle modulates the vortex street, breaking a symmetry. The parameter dependence of the modulation dynamics of vortices is investigated. © 2013 The Authors.
International conference proceedings, English - Benard-von Karman vortex street in an exciton-polariton superfluid
Hiroki Saito; Tomohiko Aioi; Tsuyoshi Kadokura
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 86, 1, 014504, Jul. 2012, Peer-reviwed, The dynamics of an exciton-polariton superfluid resonantly injected into a semiconductor microcavity are investigated numerically. The results reveal that a Benard-von Karman vortex street is generated in the wake behind an obstacle potential, in addition to the generation of quantized vortex dipoles and dark solitons. The vortex street can be observed in the presence of a disorder potential in a realistic sample, and it can be observed even in time-integrated measurements.
Scientific journal, English - Penetration of a vortex dipole across an interface of Bose-Einstein condensates
Tomohiko Aioi; Tsuyoshi Kadokura; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 85, 2, 023618, Feb. 2012, Peer-reviwed, The dynamics of a vortex dipole in a quasi-two-dimensional two-component Bose-Einstein condensate is investigated. A vortex dipole is shown to penetrate the interface between the two components when the incident velocity is sufficiently large. A vortex dipole can also disappear or disintegrate at the interface, depending on its velocity and the interaction parameters.
Scientific journal, English - Rayleigh-Taylor instability in a two-component Bose-Einstein condensate with rotational symmetry
Tsuyoshi Kadokura; Tomohiko Aioi; Kazuki Sasaki; Tetsuo Kishimoto; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 85, 1, 013602, Jan. 2012, Peer-reviwed, The interfacial instability and subsequent dynamics in a phase-separated two-component Bose-Einstein condensate with rotational symmetry are studied. When the interatomic interaction or the trap frequency is changed, the Rayleigh-Taylor instability breaks the rotational symmetry of the interface, which is subsequently deformed into nonlinear patterns including mushroom shapes.
Scientific journal, English - Controlled Generation and Manipulation of Vortex Dipoles in a Bose-Einstein Condensate
Tomohiko Aioi; Tsuyoshi Kadokura; Tetsuo Kishimoto; Hiroki Saito
PHYSICAL REVIEW X, AMER PHYSICAL SOC, 1, 2, 021003, Oct. 2011, Peer-reviwed, We propose methods to generate and manipulate vortex dipoles in an atomic Bose-Einstein condensate using Gaussian beams of red-or blue-detuned laser. Vortex dipoles with controlled velocities are shown to be created and launched by a red-detuned beam and by two blue-detuned beams. Critical beam velocities for the vortex nucleation are investigated. The launched vortex dipoles can be trapped, curved, accelerated, and decelerated by using Gaussian laser beams. Collisions between vortex dipoles are demonstrated.
Scientific journal, English - Capillary instability in a two-component Bose-Einstein condensate
Kazuki Sasaki; Naoya Suzuki; Hiroki Saito
Physical Review A - Atomic, Molecular, and Optical Physics, 83, 5, 03 May 2011, Peer-reviwed, Capillary instability and the resulting dynamics in an immiscible two-component Bose-Einstein condensate are investigated using the mean-field and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other component is dynamically unstable against breakup into droplets due to the interfacial tension arising from the quantum pressure and interactions. A heteronuclear system confined in a cigar-shaped trap is proposed for realizing this phenomenon experimentally. © 2011 American Physical Society.
Scientific journal, English - Capillary instability in a two-component Bose-Einstein condensate
Kazuki Sasaki; Naoya Suzuki; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 83, 5, 053606, May 2011, Peer-reviwed, Capillary instability and the resulting dynamics in an immiscible two-component Bose-Einstein condensate are investigated using the mean-field and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other component is dynamically unstable against breakup into droplets due to the interfacial tension arising from the quantum pressure and interactions. A heteronuclear system confined in a cigar-shaped trap is proposed for realizing this phenomenon experimentally.
Scientific journal, English - Dynamics of bubbles in a two-component Bose-Einstein condensate
Kazuki Sasaki; Naoya Suzuki; Hiroki Saito
Physical Review A - Atomic, Molecular, and Optical Physics, 83, 3, 03 Mar. 2011, Peer-reviwed, The dynamics of a phase-separated two-component Bose-Einstein condensate are investigated, in which a bubble of one component moves through the other component. Numerical simulations of the Gross-Pitaevskii equation reveal a variety of dynamics associated with the creation of quantized vortices. In two dimensions, a circular bubble deforms into an ellipse and splits into fragments with vortices, which undergo the Magnus effect. The Bénard-von Kármán vortex street is also generated. In three dimensions, a spherical bubble deforms into toruses with vortex rings. When two rings are formed, they exhibit leapfrogging dynamics. © 2011 American Physical Society.
Scientific journal, English - Dynamics of bubbles in a two-component Bose-Einstein condensate
Kazuki Sasaki; Naoya Suzuki; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 83, 3, 033602, Mar. 2011, Peer-reviwed, The dynamics of a phase-separated two-component Bose-Einstein condensate are investigated, in which a bubble of one component moves through the other component. Numerical simulations of the Gross-Pitaevskii equation reveal a variety of dynamics associated with the creation of quantized vortices. In two dimensions, a circular bubble deforms into an ellipse and splits into fragments with vortices, which undergo the Magnus effect. The Benard-von Karman vortex street is also generated. In three dimensions, a spherical bubble deforms into toruses with vortex rings. When two rings are formed, they exhibit leapfrogging dynamics.
Scientific journal, English - Benard-von Karman vortex street in a Bose-Einstein condensate
Kazuki Sasaki; Naoya Suzuki; Hiroki Saito
PS64, Jan. 2011
International conference proceedings, English - Crossover between Kelvin-Helmholtz and counter-superflow instabilities in two-component Bose-Einstein condensates
Naoya Suzuki; Hiromitsu Takeuchi; Kenichi Kasamatsu; Makoto Tsubota; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 82, 6, 063604, Dec. 2010, Peer-reviwed, Dynamical instabilities at the interface between two Bose-Einstein condensates that are moving relative to each other are investigated using mean-field and Bogoliubov analyses. Kelvin-Helmholtz instability is dominant when the interface thickness is much smaller than the wavelength of the unstable interface mode, whereas the counter-superflow instability becomes dominant in the opposite case. These instabilities emerge not only in an immiscible system but also in a miscible system where an interface is produced by external potential. Dynamics caused by these instabilities are numerically demonstrated in rotating trapped condensates.
Scientific journal, English - Spontaneous magnetic ordering in a ferromagnetic spinor dipolar Bose-Einstein condensate
Yuki Kawaguchi; Hiroki Saito; Kazue Kudo; Masahito Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 82, 4, 043627, Oct. 2010, Peer-reviwed, We study the spin dynamics of a spin-1 ferromagnetic Bose-Einstein condensate with magnetic dipole-dipole interaction (MDDI) based on the Gross-Pitaevskii and Bogoliubov theories. We find that various magnetic structures such as checkerboards and stripes emerge in the course of the dynamics due to the combined effects of spin-exchange interaction, MDDI, quadratic Zeeman and finite-size effects, and nonstationary initial conditions. However, the short-range magnetic order observed by the Berkeley group [Phys. Rev. Lett. 100, 170403 (2008)] is not fully reproduced in our calculations; the periodicity of the order differs by a factor of 3 and the checkerboard pattern eventually dissolves in the course of time. Possible reasons for the discrepancy are discussed.
Scientific journal, English - Controlling phase separation of binary Bose-Einstein condensates via mixed-spin-channel Feshbach resonance
Satoshi Tojo; Yoshihisa Taguchi; Yuta Masuyama; Taro Hayashi; Hiroki Saito; Takuya Hirano
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 82, 3, 033609, Sep. 2010, Peer-reviwed, We investigate controlled phase separation of a binary Bose-Einstein condensate in the proximity of a mixed-spin-channel Feshbach resonance in the vertical bar F = 1, m(F) = +1 > and vertical bar F = 2, mF = -1 > states of Rb-87 at a magnetic field of 9.10 G. Phase separation occurs on the lower-magnetic-field side of the Feshbach resonance while the two components overlap on the higher-magnetic-field side. The Feshbach resonance curve of the scattering length is obtained from the shape of the atomic cloud by comparison with the numerical analysis of coupled Gross-Pitaevskii equations.
Scientific journal, English - Connection between rotation and miscibility in a two-component Bose-Einstein condensate
Takayuki Shimodaira; Tetsuo Kishimoto; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 82, 1, 013647, Jul. 2010, Peer-reviwed, A two-component Bose-Einstein condensate rotating in a toroidal trap is investigated. The topological constraint depends on the density distribution of each component along the circumference of the torus, and therefore the quantization condition on the circulation can be controlled by changing the miscibility using the Feshbach resonance. We find that the system exhibits a variety of dynamics depending on the initial angular momentum when the miscibility is changed.
Scientific journal, English - Benard-von Karman Vortex Street in a Bose-Einstein Condensate
Kazuki Sasaki; Naoya Suzuki; Hiroki Saito
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 104, 15, 150404, Apr. 2010, Peer-reviwed, Vortex shedding from an obstacle potential moving in a Bose-Einstein condensate is investigated. Longlived alternately aligned vortex pairs are found to form in the wake, which is similar to the Benard von Karman vortex street in classical viscous fluids. Various patterns of vortex shedding are systematically studied and the drag force on the obstacle is calculated. It is shown that the phenomenon can be observed in a trapped system.
Scientific journal, English - Quantum Kelvin-Helmholtz instability in phase-separated two-component Bose-Einstein condensates
Hiromitsu Takeuchi; Naoya Suzuki; Kenichi Kasamatsu; Hiroki Saito; Makoto Tsubota
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 81, 9, 094517, Mar. 2010, Peer-reviwed, We theoretically study the Kelvin-Helmholtz instability in phase-separated two-component Bose-Einstein condensates using the Gross-Pitaevskii and Bogoliubov-de Gennes models. A flat interface between the two condensates is shown to deform into sawtooth or Stokes-type waves, leading to the formation of singly quantized vortices on the peaks and troughs of the waves. This scenario of interface instability in quantum fluids is quite different from that in classical fluids.
Scientific journal, English - Shear-flow Instability in Two-component Bose-Einstein Condensates
Hiromitsu Takeuchi; Naoya Suzuki; Kenichi Kasamatsu; Hiroki Saito; Makoto Tsubota
JOURNAL OF LOW TEMPERATURE PHYSICS, SPRINGER/PLENUM PUBLISHERS, 158, 3-4, 384-390, Feb. 2010, Peer-reviwed, We theoretically study Kelvin-Helmholtz instability in phase-separated two-component Bose-Einstein condensates with shear flow at T=0. The stability of the shear flow state is investigated with the Gross-Pitaevskii and the Bogoliubov-de Gennes models, compared with a hydrodynamic model. The dynamics of the instability is revealed by numerically solving the Gross-Pitaevskii equation. In the nonlinear development, singly-quantized vortices are released from the interface between the two condensates.
Scientific journal, English - Symmetry-breaking magnetization dynamics of spinor dipolar Bose-Einstein condensates
Shoichi Hoshi; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 81, 1, 013627, Jan. 2010, The symmetry-breaking magnetization dynamics of a spin-1 Bose-Einstein condensate (BEC) due to the dipole-dipole interaction are investigated using the mean-field and Bogoliubov theories. When a magnetic field is applied along the symmetry axis of a pancake-shaped BEC in the m = 0 hyperfine sublevel, transverse magnetization develops breaking the chiral or axial symmetry. A variety of magnetization patterns are formed depending on the strength of the applied magnetic field. The proposed phenomena can be observed in Rb-87 and Na-23 condensates.
Scientific journal, English - NEW PHYSICS IN DIPOLAR BOSE-EINSTEIN CONDENSATES
Yuki Kawaguchi; Hiroki Saito; Masahito Ueda
LASER SPECTROSCOPY, WORLD SCIENTIFIC PUBL CO PTE LTD, 29-+, 2010, We study atomic Bose-Einstein condensates (BECs) with the magnetic dipole-dipole interaction. The long-range and anisotropic nature of the interaction causes anisotropic collapse in a spin-polarized BEC, ferrofluidity and supersolidity in a two-component BEC, and spontaneous circulation in a spinor BEC.
International conference proceedings, English - Rayleigh-Taylor instability and mushroom-pattern formation in a two-component Bose-Einstein condensate
Kazuki Sasaki; Naoya Suzuki; Daisuke Akamatsu; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 80, 6, 063611, Dec. 2009, Peer-reviwed, The Rayleigh-Taylor instability at the interface in an immiscible two-component Bose-Einstein condensate is investigated using the mean field and Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the interface and mushroom patterns are formed. Quantized vortex rings and vortex lines are then generated around the mushrooms. The Rayleigh-Taylor instability and mushroom-pattern formation can be observed in a trapped system.
Scientific journal, English - Spin-dependent inelastic collisions in spin-2 Bose-Einstein condensates
Satoshi Tojo; Taro Hayashi; Tatsuyoshi Tanabe; Takuya Hirano; Yuki Kawaguchi; Hiroki Saito; Masahito Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 80, 4, 042704, Oct. 2009, Peer-reviwed, We studied spin-dependent two-body inelastic collisions in F=2 (87)Rb Bose-Einstein condensates both experimentally and theoretically. The (87)Rb condensates were confined in an optical trap and selectively prepared in various spin states in the F=2 manifold at a magnetic field of 3.0 G. The measured atom loss rates depend on the spin states of colliding atoms. We measured two fundamental loss coefficients for two-body inelastic collisions with total spins of 0 and 2. The loss coefficients determine the loss rates of all the spin pairs. The experimental results for mixtures of all spin combinations are in good agreement with numerical solutions of the Gross-Pitaevskii equations that include the effect of a magnetic field gradient.
Scientific journal, English - Comment On "Fragmented Metastable States Exist in an Attractive Bose-Einstein Condensate for Atom Numbers Well Above the Critical Number of the Gross-Pitaevskii Theory"
Hiroki Saito
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 103, 1, 018901, Jul. 2009, Peer-reviwed, A Comment on the Letter by Lorenz S. Cederbaum, Alexej I. Streltsov, and Ofir E. Alon, [Phys. Rev. Lett. 100, 040402 (2008)].
Scientific journal, English - Ferrofluidity in a Two-Component Dipolar Bose-Einstein Condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 102, 23, 230403, Jun. 2009, Peer-reviwed, It is shown that the interface in a two-component Bose-Einstein condensate (BEC) with a dipole-dipole interaction spontaneously develops patterns similar to those formed in a ferrofluid. Hexagonal, labyrinthine, solitonlike structures, and hysteretic behavior are numerically demonstrated. Superflow is found to circulate around the hexagonal pattern at rest, offering evidence of supersolidity. The system sustains persistent current with a vortex line pinned by the hexagonal pattern. These phenomena may be realized using a (52)Cr BEC.
Scientific journal, English - Coherent collapses of dipolar Bose-Einstein condensates for different trap geometries
J. Metz; T. Lahaye; B. Froehlich; A. Griesmaier; T. Pfau; H. Saito; Y. Kawaguchi; M. Ueda
NEW JOURNAL OF PHYSICS, IOP PUBLISHING LTD, 11, 055032, May 2009, Peer-reviwed, We experimentally investigate the collapse dynamics of dipolar Bose-Einstein condensates of chromium atoms in different harmonic trap geometries, from prolate to oblate. The evolutions of the condensates in the unstable regime are compared with three-dimensional simulations of the Gross-Pitaevskii equation including three-body losses. In order to probe the phase coherence of collapsed condensates, we induce the collapse in several condensates simultaneously and let them interfere.
Scientific journal, English - Magnetization of a half-quantum vortex in a spinor Bose-Einstein condensate
Shoichi Hoshi; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 78, 5, 053618, Nov. 2008, Peer-reviwed, Magnetization dynamics of a half-quantum vortex in a spin-1 Bose-Einstein condensate with a ferromagnetic interaction are investigated by mean-field and Bogoliubov analyses. The transverse magnetization is shown to break the axisymmetry and form threefold domains. This phenomenon originates from the topological structure of the half-quantum vortex and spin conservation.
Scientific journal, English - Spin-vortex nucleation in a Bose-Einstein condensate by a spin-dependent rotating trap
Hiroki Chiba; Hiroki Saito
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 78, 4, 043602, Oct. 2008, Peer-reviwed, A method to produce a spin-dependent rotating potential using near-resonant circularly polarized laser beams is proposed. It is shown that half-quantum vortices are nucleated in a spinor Bose-Einstein condensate (BEC) with an antiferromagnetic interaction. In contrast to the vortex nucleation in a scalar BEC, the spin-vortex nucleation occurs at a low rotation frequency (similar or equal to 0.1 omega(perpendicular to) with omega(perpendicular to) being the radial trap frequency) in a short nucleation time similar or equal to 50 ms without dissipation. A method for nondestructive measurement of half-quantum vortices is discussed.
Scientific journal, English - Dynamical Casimir effect for magnons in a spinor Bose-Einstein condensate
Hiroki Saito; Hiroyuki Hyuga
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 78, 3, 033605, Sep. 2008, Peer-reviwed, Magnon excitation in a spinor Bose-Einstein condensate by a driven magnetic field is shown to have a close analogy with the dynamical Casimir effect. A time-dependent external magnetic field amplifies quantum fluctuations in the magnetic ground state of the condensate, leading to magnetization of the system. The magnetization occurs in a direction perpendicular to the magnetic field breaking the rotation symmetry. This phenomenon is numerically demonstrated and the excited quantum field is shown to be squeezed.
Scientific journal, English - d-wave collapse and explosion of a dipolar Bose-Einstein condensate
T. Lahaye; J. Metz; B. Froehlich; T. Koch; M. Meister; A. Griesmaier; T. Pfau; H. Saito; Y. Kawaguchi; M. Ueda
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 101, 8, 080401, Aug. 2008, Peer-reviwed, We investigate the collapse dynamics of a dipolar condensate of (52)Cr atoms when the s-wave scattering length characterizing the contact interaction is reduced below a critical value. A complex dynamics, involving an anisotropic, d-wave symmetric explosion of the condensate, is observed. The atom number decreases abruptly during the collapse. We find good agreement between our experimental results and those of a numerical simulation of the three-dimensional Gross-Pitaevskii equation, including contact and dipolar interactions as well as three-body losses. The simulation indicates that the collapse induces the formation of two vortex rings with opposite circulations.
Scientific journal, English - Kibble-Zurek Mechanism in Magnetization of a Spinor Bose-Einstein Condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
Proceedings of the 9th international symposium on foundations of quantum mechanics in the light of new technology, 33, 2008
International conference proceedings, English - Stabilization of a Bose-Einstein droplet by hyperfine Rabi oscillations
Hiroki Saito; Randall G. Hulet; Masahito Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 76, 5, 053619, Nov. 2007, Peer-reviwed, A self-trapped Bose-Einstein condensate is shown to be stabilized in two-dimensional free space by Rabi oscillations between two hyperfine states which make an effective interatomic interaction oscillate in time. The stabilization mechanism is elucidated by using a two-component Gross-Pitaevskii equation combined with a variational analysis. The parameter regime of stability is investigated.
Scientific journal, English - Kibble-Zurek mechanism in a quenched ferromagnetic Bose-Einstein condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 76, 4, 043613, Oct. 2007, Peer-reviwed, It is shown that spin vortices are created through the Kibble-Zurek mechanism in the quantum phase transition of a spin-1 ferromagnetic Bose-Einstein condensate when the applied magnetic field is quenched to below a critical value. It is also shown that the spin correlation functions have finite correlation lengths, and that the magnetization at widely separated positions grows in random directions, resulting in spontaneous creation of spin vortices. We numerically confirm the scaling laws that the winding number of spin vortices is proportional to the square root of the length of a closed path and, for a slow quench, is proportional to tau(-1/6)(Q) with tau(Q) being the quench time. The relevance of spin conservation to the Kibble-Zurek mechanism is discussed.
Scientific journal, English - Symmetry breaking in scalar, spinor, and rotating Bose-Einstein condensates
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
NUCLEAR PHYSICS A, ELSEVIER SCIENCE BV, 790, 737C-741C, Jun. 2007, A gaseous Bose-Einstein condensate is shown to exhibit a rich variety of symmetry breakings accompanied by quantum phase transitions. We review our recent studies from the viewpoint of spontaneous symmetry breaking.
Scientific journal, English - Can spinor dipolar effects be observed in Bose-Einstein condensates?
Yuki Kawaguchi; Hiroki Saito; Masahito Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 98, 11, Mar. 2007, Peer-reviwed, Weak dipolar effects in atomic Bose-Einstein condensates (BECs) have recently been predicted to develop spin textures. However, observation of the spin textures requires us to decrease the magnetic field down to similar to 10 mu G for spin-1 alkali BECs, so that they are not washed out by the Zeeman effect. We present a scheme to observe the magnetic dipole-dipole interaction in alkali BECs under a realistic magnetic field of similar to 100 mG. Our scheme enables us to extract genuine dipolar effects and should apply also to Cr-52 BECs.
Scientific journal, English - Topological defect formation in a quenched ferromagnetic Bose-Einstein condensates
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 75, 1, 013621, Jan. 2007, We study the dynamics of the quantum phase transition of a ferromagnetic spin-1 Bose-Einstein condensate (BEC) from the polar phase to the broken-axisymmetry phase by changing magnetic field, and find the spontaneous formation of spinor domain walls followed by the creation of polar-core spin vortices. We also find that the spin textures depend very sensitively on the initial noise distribution, and that an anisotropic and colored initial noise is needed to reproduce the Berkeley experiment [Sadler et al., Nature (London) 443, 312 (2006)]. The dynamics of vortex nucleation and the number of created vortices depend also on the manner in which the magnetic field is changed. We point out an analogy between the formation of spin vortices from domain walls in a spinor BEC and that of vortex-antivortex pairs from dark solitons in a scalar BEC.
Scientific journal, English - Broken-axisymmetry phase of a spin-1 ferromagnetic Bose-Einstein condensate
Keiji Murata; Hiroki Saito; Masahito Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 75, 1, 013607, Jan. 2007, Peer-reviwed, A spin-1 ferromagnetic Bose-Einstein condensate subject to a certain magnetic field exhibits a broken-axisymmetry phase in which the magnetization tilts against the applied magnetic field due to the competition between ferromagnetism and linear and quadratic Zeeman effects. The Bogoliubov analysis shows that in this phase two Goldstone modes associated with U(1) and SO(2) symmetry breakings exist, in which phonons and magnons are coupled to restore the two broken symmetries.
Scientific journal, English - Spontaneous circulation in ground-state spinor dipolar Bose-Einstein condensates
Yuki Kawaguchi; Hiroki Saito; Masahito Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 97, 13, 130404, Sep. 2006, Peer-reviwed, We report on a study of the spin-1 ferromagnetic Bose-Einstein condensate with magnetic dipole-dipole interactions. By solving the nonlocal Gross-Pitaevskii equations for this system, we find three ground-state phases. Moreover, we show that a substantial orbital angular momentum accompanied by chiral symmetry breaking emerges spontaneously in a certain parameter regime. We predict that all these phases can be observed in the spin-1 Rb-87 condensate by changing the number of atoms or the trap frequency.
Scientific journal, English - Stabilization of a matter-wave droplet in free space by feedback control of interatomic interactions
Hiroki Saito; Masahito Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 74, 2, 023602, Aug. 2006, Peer-reviwed, A Bose-Einstein condensate in three-dimensional free space is known to be unstable against expansion or collapse if the scattering length of atoms is constant. We propose a method to produce a stable self-trapped condensate in which nondestructive measurement of the condensate's peak density is used to perform feedback control of the scattering length. The stability is shown to be robust against experimental imperfections in the measurements.
Scientific journal, English - Critical fluctuations in a soliton formation of attractive Bose-Einstein condensates
R Kanamoto; H Saito; M Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 73, 3, 033611, Mar. 2006, Peer-reviwed, We employ mean-field, Bogoliubov and many-body theories to study critical fluctuations in the position and momentum of a Bose-Einstein condensate whose translation symmetry is spontaneously broken due to attractive interactions. In a homogeneous system, the many-body ground state of the symmetry-preserving Hamiltonian is very fragile against superposition of low-lying states, while the mean-field theory predicts a stable bright soliton which spontaneously breaks translation symmetry. We show that weak symmetry-breaking perturbations cause the translation-symmetric many-body ground state to cross over to a many-body bright soliton. We argue that the center-of-mass fluctuations in the soliton state arise primarily from the depletion of the condensate to translation modes. We develop an extended mean-field theory to analytically reproduce these results obtained by the exact diagonalization method.
Scientific journal, English - Einstein-de Haas effect in dipolar Bose-Einstein condensates
Y Kawaguchi; H Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 96, 8, 080405, Mar. 2006, Peer-reviwed, The general properties of the order parameter for a dipolar spinor Bose-Einstein condensate are discussed based on symmetries of interactions. An initially spin-polarized dipolar condensate is shown to dynamically generate a nonsingular vortex via spin-orbit interactions-a phenomenon reminiscent of the Einstein-de Haas effect in ferromagnets.
Scientific journal, English - Breaking of chiral symmetry and spontaneous rotation in a spinor Bose-Einstein condensate
H Saito; Y Kawaguchi; M Ueda
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 96, 6, 065302, Feb. 2006, We show that a spin-1 Bose-Einstein condensate with ferromagnetic interactions spontaneously generates a topological spin texture, in which the m=+/- 1 components of the magnetic sublevels form vortices with opposite circulations. This phenomenon originates from an interplay between ferromagnetic interactions and spin conservation.
Scientific journal, English - Symmetry breaking in Bose-Einstein condensates
Masahito Ueda; Yuki Kawaguchi; Hiroki Saito; Rina Kanamoto; Tatsuya Nakajima
ATOMIC PHYSICS 20, AMER INST PHYSICS, 869, 165-+, 2006, Peer-reviwed, A gaseous Bose-Einstein condensate (BEC) offers an ideal testing ground for studying symmetry breaking, because a trapped BEC system is in a mesoscopic regime, and situations exist under which symmetry breaking may or may not occur. Investigating this problem can explain why mean-field theories have been so successful in elucidating gaseous BEC systems and when many-body effects play a significant role. We substantiate these ideas in four distinct situations: namely, soliton formation in attractive BECs, vortex nucleation in rotating BECs, spontaneous magnetization in spinor BECs, and spin texture formation in dipolar BECs.
International conference proceedings, English - Diagnostics for the ground-state phase of a spin-2 Bose-Einstein condensate
Hiroki Saito; Masahito Ueda
Physical Review A - Atomic, Molecular, and Optical Physics, 72, 5, Nov. 2005, Peer-reviwed, We propose a method of using spin exchange dynamics to determine the coefficient of the spin-singlet pair term of a spin-2 Bose-Einstein condensate (BEC) by preparing the initial populations in the magnetic sublevels 0 and ±2 with appropriate relative phases. This method is suitable for a BEC with a short lifetime, since only the initial change in the population of each magnetic sublevel is needed. Our method therefore enables the determination of the ground-state phase of a spin-2 Rb87 BEC at zero magnetic field, which is considered to lie in the immediate vicinity of the boundary between the antiferromagnetic and cyclic phases. We propose a scheme to prepare the initial state in which the relative phases between the magnetic sublevels are controlled. We also propose a simple scheme to distinguish between the antiferromagnetic and cyclic phases under a situation of very low bias magnetic field. © 2005 The American Physical Society.
Scientific journal, English - Spontaneous magnetization and structure formation in a spin-1 ferromagnetic Bose-Einstein condensate
Hiroki Saito; Masahito Ueda
Physical Review A - Atomic, Molecular, and Optical Physics, 72, 2, Aug. 2005, Peer-reviwed, Motivated by recent experiments involving the nondestructive imaging of magnetization of a spin-1 \\par\\parRb87\\par\\par Bose gas [J. M. Higbie, Phys. Rev. Lett., 95, 050401 (2005)], we address the question of how the spontaneous magnetization of a ferromagnetic Bose-Einstein condensate occurs in a spin-conserving system. Due to competition between the ferromagnetic interaction and the total spin conservation, various spin structures such as staggered magnetic domains and helical and concentric ring structures are formed, depending on the geometry of the trapping potential. © 2005 The American Physical Society.
Scientific journal, English - Symmetry breaking and enhanced condensate fraction in a matter-wave bright soliton
R Kanamoto; H Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 94, 9, 090404, Mar. 2005, Peer-reviwed, An exact diagonalization study reveals that a matter-wave bright soliton and the Goldstone mode are simultaneously created in a quasi-one-dimensional attractive Bose-Einstein condensate by superpositions of quasidegenerate low-lying many-body states. Upon formation of the soliton the maximum eigenvalue of the single-particle density matrix increases dramatically, indicating that a fragmented condensate converts into a single condensate as a consequence of the breaking of translation symmetry.
Scientific journal, English - Many-body analysis of the Hess-Fairbank effect in one-dimensional Bose-Einstein condensates with attractive interactions
R Kanamoto; H Saito; M Tsubota; M Ueda
JOURNAL OF LOW TEMPERATURE PHYSICS, SPRINGER/PLENUM PUBLISHERS, 138, 3-4, 681-686, Feb. 2005, Peer-reviwed, In terms of the many-body energy spectrum obtained by a diagonalization of Hamiltonian, we discuss the Hess-Fiarbank effect in an attractive Bose-Einstein condensate on a one-dimensional ring. Depending on the strength of interaction and the rotational frequency of the container, there exist two characteristic features in the spectrum. We argue that the existence of a regime of a huge number of low-lying levels causes the smearing of the plateau of the quantized circulation in contrast to conventional superfluids with repulsive interaction.
Scientific journal, English - Emergence of Bloch bands in a rotating Bose-Einstein condensate
H Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 93, 22, 220402, Nov. 2004, A rotating Bose-Einstein condensate is shown to exhibit a Bloch band structure even in the absence of a periodic potential. Vortices enter the condensate via Bragg reflection if the frequency of a rotating drive is adiabatically increased or decreased, or if the interaction is adiabatically changed at a constant rotating drive. A localized state analogous to a gap soliton in a periodic system is predicted to occur near the edge of the Brillouin zone.
Scientific journal, English - Bose-Einstein droplet in free space
H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 70, 5, 053610, Nov. 2004, A "gaseous droplet"-a stable gas that coheres by itself in free space-is shown to be produced with a Bose-Einstein condensate. Collapse and expansion of the droplet are suppressed by rapid oscillations of the interatomic interaction between attractive and repulsive through, e.g., the Feshbach resonance. Energy dissipation, which is present in realistic situations, is found to play a crucial role in suppressing dynamical instabilities that destabilize the droplet.
Scientific journal, English - Split-merge cycle, fragmented collapse, and vortex disintegration in rotating Bose-Einstein condensates with attractive interactions
H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 69, 1, 013604, Jan. 2004, The dynamical instabilities and ensuing dynamics of singly and doubly quantized vortex states of Bose-Einstein condensates with attractive interactions are investigated using full three-dimensional numerical simulations of the Gross-Pitaevskii equation. With increasing the strength of attractive interactions, a series of dynamical instabilities such as quadrupole, dipole, octupole, and monopole instabilities emerge. The most prominent instability depends on the strength of interactions, the geometry of the trapping potential, and deviations from the axisymmetry due to external perturbations. Singly quantized vortices split into two clusters and subsequently undergo split-merge cycles in a pancake-shaped trap, whereas the split fragments immediately collapse in a spherical trap. Doubly quantized vortices are always unstable to disintegration of the vortex core. If we suddenly change the strength of interaction to within a certain range, the vortex splits into three clusters, and one of the clusters collapses after a few split-merge cycles. The vortex split can be observed using a current experimental setup of Leanhardt et at. [Phys. Rev. Lett. 89, 190403 (2002)].
Scientific journal, English - Bright Solitons in a Two-Dimensional Bose-Einstein Condensate
Hiroki Saito; Masahito Ueda
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 72, 140-143, Nov. 2003, Peer-reviwed, We present two novel phenomena concerning bright solitons in a gaseous Bose-Einstein condensate with attractive interatomic interactions. (1) For the strength of interaction larger than a critical one, a vortex splits into two clusters (solitons) via the quadrupole dynamical instability. (2) A soliton can be stabilized in 2D free space by making the strength of interactions oscillate rapidly.
Scientific journal, English - A Consistent Picture of a Collapsing Bose-Einstein Condensate
Masahito Ueda; Hiroki Saito
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 72, 127-133, Nov. 2003, Peer-reviwed, We present a consistent picture of the recent JILA experiments on the collapse of a Bose-Einstein condensate (BEC) [E. A. Donley, et al.: Nature 412 (2001) 295] based on a generalized Gross-Pitaevskii equation that incorporates the effect of a three-body loss. The questions we address in this paper are: (1) Why does a BEC survive, albeit partially, after the collapse? (2) Why does the number of the remnant BEC atoms observed at JILA exceed the critical value? (3) What is the origin of the atom burst? (4) What is the origin of the atom jet and is it coherent? We review our predictions on pattern formation in the course of collapse and on the split instability of vortices that can test our collapsing theory.
Scientific journal, English - Measurement-induced spin squeezing in a cavity
H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 68, 4, 043820, Oct. 2003, Spin squeezing of an ensemble of N atoms in a high-Q cavity is enhanced by continuous measurement of photons in the cavity. A degree of spin squeezing proportional to N-1/3 is achieved as a quasi-steady-state over a broad set of initial states of atoms and photons. Our method of spin squeezing is robust against the imperfect photodetection efficiency in current experiments.
Scientific journal, English - Stability of the quantized circulation of an attractive Bose-Einstein condensate in a rotating torus
R Kanamoto; H Saito; M Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 68, 4, 043619, Oct. 2003, We investigate rotational properties of a system of attractive bosons confined in a one-dimensional torus. Two kinds of ground states, uniform-density and bright soliton, are obtained analytically as functions of the strength of interaction and of the rotational frequency of the torus. The quantization of circulation appears in the uniform-density state, but disappears upon formation of the soliton. By comparing the results of exact diagonalization with those predicted by the Bogoliubov theory, we show that the Bogoliubov theory is valid at absolute zero over a wide range of parameters. At finite temperatures we employ the exact diagonalization method to examine how thermal fluctuations smear the plateaus of the quantized circulation. Finally, by rotating the system with an axisymmetry-breaking potential, we clarify the process by which the quantized circulation becomes thermodynamically stabilized.
Scientific journal, English - Stability of the quantized circulation of an attractive Bose-Einstein condensate in a rotating torus
Rina Kanamoto; Hiroki Saito; Masahito Ueda
Physical Review A - Atomic, Molecular, and Optical Physics, American Physical Society, 68, 4 B, 043619/12, 2003, The rotational properties of one-dimensional bosons with attractive interactions confined in a rotating torus trap were studied. The ground-state wave function was derived analytically within the MFT as a function of the strength of interaction γ and of the rotational frequency of the torus Ω. A uniform-density solution and a bright-soliton one were found to cross over each other smoothly. In order to investigate the validity of the Bogoliubov theory, the excitation spectrum obtained by the Bogoliubov theory was compared to that obtained by the exact diagonalization of the many-body Hamiltonian. It was observed that the MFT well describes the ground state and the low-lying excited states.
Scientific journal, English - Quantum phase transition in one-dimensional Bose-Einstein condensates with attractive interactions
R Kanamoto; H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 67, 1, 013608, Jan. 2003, Motivated by the recent development of the Feshbach technique, we studied the ground and low-lying excited states of attractive Bose-Einstein condensates on a one-dimensional ring as a function of the strength of interactions. The Gross-Pitaevskii mean-field theory predicts a quantum phase transition between a uniform condensate and a bright soliton, and a gapless singular cusp in the Bogoliubov excitation spectrum at the critical point. However, the exact diagonalization reveals the presence of an energy gap at the critical point, where the singularity is smeared by quantum fluctuations.
Scientific journal, English - Dynamically stabilized bright solitons in a two-dimensional Bose-Einstein condensate
H Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 90, 4, 040403, Jan. 2003, We demonstrate that a matter-wave bright soliton can be stabilized in 2D free space by causing the strength of interactions to oscillate rapidly between repulsive and attractive by using, e.g., Feshbach resonance.
Scientific journal, English - Split instability of a vortex in an attractive Bose-Einstein condensate
H Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 89, 19, 190402, Nov. 2002, An attractive Bose-Einstein condensate with a vortex splits into two pieces via the quadrupole dynamical instability, which arises at a weaker strength of interaction than the monopole and the dipole instabilities. The split pieces subsequently unite to restore the original vortex or collapse.
Scientific journal, English - Dynamical Casimir effect without boundary conditions
H Saito; H Hyuga
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 65, 5, 053804, May 2002, The moving-mirror problem is microscopically formulated without invoking the external boundary conditions. The moving mirrors are described by the quantized matter field interacting with the photon field, forming dynamical cavity polaritons: photons in the cavity are dressed by electrons in the moving mirrors. The effective Hamiltonian for the polariton is derived, and corrections to the results based on the external boundary conditions are discussed.
Scientific journal, English - Mean-field analysis of collapsing and exploding Bose-Einstein condensates
H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 65, 3, 033624, Mar. 2002, The dynamics of collapsing and exploding Bose-Einstein condensates caused by a sudden switch of interactions from repulsive to attractive are studied by numerically integrating the Gross-Pitaevskii equation with atomic loss for an axially symmetric trap. We investigate the decay rate of condensates and the phenomena of bursts and jets of atoms, and compare our results with those of the experiments performed by E. A. Donley et al. [Nature (London) 412, 295 (2001)]. Our study suggests that the condensate decay and the burst production is due to local intermittent implosions in the condensate, and that atomic clouds of bursts and jets are coherent. We also predict nonlinear pattern formation caused by the density instability of attractive condensates.
Scientific journal, English - Power laws and collapsing dynamics of a trapped Bose-Einstein condensate with attractive interactions
H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 63, 4, 043601, Apr. 2001, The critical behavior of collective modes and the collapsing dynamics of trapped Bose-Einstein condensates with attractive interactions are studied analytically and numerically. The time scales of these dynamics both below and above the critical point of the collapse are found to obey power laws with a single parameter of N/N-c-1, where N is the number of condensate atoms and N-c is the critical number. The collapsing condensate eventually undergoes rapid implosion, which occurs several times intermittently, and then the implosion turns to an explosion. The release energy of the explosion is found to be proportional to the square of the interaction strength, inversely proportional to the three-body recombination rate, and independent of the number of condensate atoms and the trap frequency.
Scientific journal, English - Intermittent implosion and pattern formation of trapped Bose-Einstein condensates with an attractive interaction
H Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 86, 8, 1406-1409, Feb. 2001, The collapsing dynamics of a trapped Bose-Einstein condensate with attractive interaction are revealed to exhibit two previously unknown phenomena. During the collapse, the condensate undergoes a series of rapid implosions that occur intermittently within a very small region. When the sign of the interaction is suddenly switched from repulsive to attractive, e.g., by the Feshbach resonance, density fluctuations grow to form various patterns such as a shell structure.
Scientific journal, English - First- and second-order coherence of scattered laser light from a trapped Bose-Einstein condensate
H Saito; M Ueda
PHYSICAL REVIEW A, AMERICAN PHYSICAL SOC, 60, 5, 3990-3998, Nov. 1999, The second-order coherence of photons scattered from a trapped Bose-Einstein condensate is found to be enhanced for the scattering angles that are either the same or symmetrical with respect to the direction of laser propagation. The enhancement occurs periodically with respect to the time interval between photons, and becomes less and less pronounced with increasing the strength of the interaction between atoms. [S1050-2947(99)01011-2].
Scientific journal, English - A variational sum-rule approach to collective excitations of a trapped Bose-Einstein condensate
T Kimura; H Saito; M Ueda
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOCIETY JAPAN, 68, 5, 1477-1480, May 1999, It is found that combining an excitation-energy sum rule with Fetter's trial wave function gives almost exact low-lying collective-mode frequencies of a trapped Bose-Einstein condensate at zero temperature.
English - Squeezed few-photon states of the field generated from squeezed atoms
H Saito; M Ueda
PHYSICAL REVIEW A, AMER PHYSICAL SOC, 59, 5, 3959-3974, May 1999, This paper develops a method of manipulating the squeezed atom state to generate a few-photon state whose phase or photon-number fluctuations are prescribed at our disposal. The squeezed-atom state is a collective atomic state whose quantum fluctuations in population difference or collective dipole are smaller than those of the coherent atom state. It is shown that the squeezed-atom state can be generated by the interaction of atoms with a coherent state of the electromagnetic field, and that it can be used as a tunable source of squeezed radiation. A variety of squeezed states, including the photon-number squeezed state and the phase squeezed state, can be produced by manipulating the atomic state. This is owing to the fact that quantum-statistical information of the atomic state is faithfully transferred to that of the photon state. Possible experimental situations to implement our theory are discussed. [S1050-2947(99)02905-4].
Scientific journal, English - Quantum-controlled few-photon state generated by squeezed atoms
K Saito; M Ueda
PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 79, 20, 3869-3872, Nov. 1997, General principles and experimental schemes for generating a desired few-photon state from an aggregate of squeezed atoms are presented. Quantum-statistical information of the collective atomic dipole is found to be faithfully transferred to the photon state even in a few-photon regime. The controllability of few-photon states is shown to increase with increasing the number of squeezed atoms.
Scientific journal, English - The dynamical Casimir effect for an oscillating dielectric model
H Saito; H Hyuga
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 65, 11, 3513-3523, Nov. 1996, Dynamical Casimir effects caused by a moving mirror and a varying dielectric medium are studied in the effective Hamiltonian approach. The explicit form of the effective Hamiltonian for the uniform, step-wise, and time-dependent dielectric model is derived in addition to that for the moving mirror model. The resonant properties of induced photons for both models are considered and it is found that in contrast to the moving mirror case, the inter-mode transition for the dielectric case is suppressed between the odd-odd levels and between the even-even levels. The effects of dissipation are also taken into account by the master equation. For numerical analyses, a convenient method to integrate the time evolution is proposed.
Scientific journal, English - Relaxation of Schrodinger cat states and displaced thermal states in a density operator representation
H Saito; H Hyuga
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 65, 6, 1648-1654, Jun. 1996, Damping of quantum superposition of displaced states such as a Schrodinger cat state and a displaced thermal state interacting with a thermal reservoir is studied in a density operator formalism. The master equation approach is employed and the solution is shown to be factorized to a thermal density operator and displacement operators. This formalism is applied to the cat generating experiment proposed by Brune et al. [Phys. Rev. A 45 (1992) 5193]; and the field evolution is obtained analytically.
Scientific journal, English - Photon emission from a time-varying dielectric medium in a cavity
H Saito; H Hyuga
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 65, 5, 1139-1142, May 1996, Field evolution in a cavity including a time-varying dielectric is studied by determining the effective Hamiltonian. For a uniform dielectric, the Hamiltonian is obtained explicitly, and we use it to discuss photon creation in the case of an oscillating dielectric constant. It is shown that the mode amplification is similar to that in the case of a moving mirror, but the intermode transition is suppressed. This property enables us to amplify a selected mode alone, unlike in the moving mirror case.
Scientific journal, English
MISC
- 19aBK-10 Rabi Oscillation between Zeeman States in ^<87>Rb Bose-Einstein Condensate
Okada R; Nabeta K; Torii A; Takahashi M; Eto Y; Kunimi M; Saito H; Hirano T
The Physical Society of Japan (JPS), 2016, Meeting Abstracts of the Physical Society of Japan, 71, 0, 632-632, Japanese, 2189-079X, 110010056666, AA12721570 - 20pBR-7 Flow and current in muti-component cold atomic gases
Eto Y; Takahashi M; Hirano T; Kunimi M; Saito H
The Physical Society of Japan (JPS), 2016, Meeting Abstracts of the Physical Society of Japan, 71, 0, 1680-1681, Japanese, 2189-079X, 110010057667, AA12721570 - Non-equilibrium dynamics induced by miscibility control in binary Bose-Einstein condensates
Eto Yujiro; Takahashi Masahiro; Kunimi Masaya; Saito Hiroki; Hirano Takuya
<p>多成分流体の空間的な構造形成は、非平衡過程や非線型現象を理解する上で重要な効果である。我々は、2成分ボース・アインシュタイン凝縮体の混和性を制御することにより、不安定な空間構造を持つ混ざり合う性質の2成分凝縮体を生成し、パターン形成ダイナミクスを観測することに成功した。発表では、混和性制御の方法や実験結果の詳細について紹介する。</p>, The Physical Society of Japan, 2016, Meeting Abstracts of the Physical Society of Japan, 71, 0, 505-505, Japanese, 130006246180 - 18aBA-5 Collision and oscillation damping in multicomponent Bose-Einstein condensates
Eto Y; Takahashi M; Okada R; Nabeta K; Kunimi M; Saito H; Hirano T
The Physical Society of Japan (JPS), 16 Sep. 2015, 日本物理学会講演概要集, 70, 2, 550-550, Japanese, 2189-079X, 110010030921, AA12721570 - 微弱な磁気双極子相互作用によるボース・アインシュタイン凝縮体 スピンの空間構造形成：磁性気体としての冷却Rb原子
衛藤雄二郎; 斎藤弘樹; 平野琢也
We observed the spin texture formation and the spatial modulation of the longitudinal magnetization in a spin-2 ^<87>Rb Bose-Einstein condensate. The observed results are compared with numerical simulations of the Gross-Pitaevskii equation, which are the effects due to the magnetic dipole-dipole interaction. These results show that the magnetic dipole-dipole interaction has significant effects even on spinor condensates of alkali metal atoms., The Physical Society of Japan (JPS), Aug. 2015, 日本物理学会誌, 70, 8, 614-619, Japanese, Invited, Introduction other, 0029-0181, 110009976843, AN00196952 - 22pAG-4 Stability of the spin domain in two-component Bose-Einstein condensates
Tokita H; Kunimi M; Okada R; Nabeta K; Eto Y; Saito H; Hirano T
The Physical Society of Japan (JPS), 21 Mar. 2015, 日本物理学会講演概要集, 70, 1, 665-665, Japanese, 2189-079X, 110009990721, AA12721570 - 磁気双極子相互作用するボース・アインシュタイン凝縮体
斎藤弘樹; 川口由紀; 上田正仁
Feb. 2011, 固体物理, 46, 21, Japanese, Introduction other - 磁気双極子相互作用するボース・アインシュタイン凝縮体
川口由紀; 斎藤弘樹; 上田正仁
Magnetic dipole-dipole interaction in atomic Bose-Einstein condensates (BECs) can induce spin textures, even though it is weaker than other interactions. The key feature of the dipolar interaction is that it is spin-orbit coupling interaction which conserves total angular momentum. Therefore, at extremely low magnetic field, an initially spin-polarized BEC starts rotating spontaneously. Moreover, spin textures develop in the ground state, leading to spontaneous mass current. Such dipolar effect should be observed in a spinor BEC of ^<87>Rb atoms., The Physical Society of Japan (JPS), Aug. 2009, 日本物理学会誌, 64, 8, 623-627, Japanese, Introduction other, 0029-0181, 110007360062, AN00196952 - 磁性超流動体におけるスーパーノヴァ
斎藤弘樹; 川口由紀; 上田正仁
岩波書店, 2009, 科学, 79, 2, 139-141, Japanese, Introduction other, 0022-7625, 40016447141, AN00036810 - ひとりでにできる量子渦
斎藤弘樹
2007, パリティ誌, 22, 1, 13-14, Japanese, Introduction other - Relaxation of Schrodinger Cat States and Displaced Thermal States in a Density Operator Formalism
Hiroki Saito; Hiroyuki Hyuga
1996, Journal of the Phys. souty of Japan 65, 65, 6, 1648-1654, 0031-9015, 110001979926
Books and other publications
- 物理学者、機械学習を使う：第２章 量子多体系とニューラルネットワーク
斎藤弘樹
Scholarly book, Japanese, Joint work, 第２章 量子多体系とニューラルネットワーク, 朝倉書店, Oct. 2019 - Electromagnetic, Magnetostatic, and Exchange-Interaction Vortices in Confined Magnetic Structures
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
English, Joint work, Topological defect formation in spinor and dipolar Bose-Einstein condensates, Transworld Research Network, 2008 - Emergent Nonlinear Phenomena in Bose-Einstein Condensates
Masahito Ueda; Hiroki Saito
English, Joint work, Vortex lattices in Bose-Einstein condensates: Theory, Springer, 2007
Lectures, oral presentations, etc.
- 2 次元2 成分量子乱流におけるエンストロフィーカスケード
小林凌; 斎藤弘樹
Oral presentation, 日本物理学会第７９回年次大会
18 Sep. 2024 - 二成分超流動体の定常乱流におけるコルモゴロフ則
門倉強; 斎藤弘樹
Oral presentation, 日本物理学会第７９回年次大会
18 Sep. 2024 - Quantum droplet in a spinor dipolar Bose-Einstein condensate
Shaoxiong Li; Hiroki Saito
Oral presentation, 日本物理学会第７９回年次大会
16 Sep. 2024 - Spontaneous Creation of Skyrmions in a Two-Component Bose- Einstein Condensate
Rabeea Kiran; Hiroki Saito
Oral presentation, 日本物理学会第７９回年次大会
16 Sep. 2024 - Ground and metastable states in a mixture of spin-1 and spin-2 BECs of 87Rb
Uyen Le; Hiroki Saito
Oral presentation, 日本物理学会 2024年春季大会
19 Mar. 2024 - 量子乱流におけるユニタリーなエネルギー散逸
門倉強; 斎藤弘樹
Oral presentation, 日本物理学会第７８回年次大会
18 Sep. 2023 - バブル型トラップ中で回転するBECにおけるRossby-Haurwitz波
斎藤弘樹; 林正純
Oral presentation, 日本物理学会第７８回年次大会
18 Sep. 2023 - Mixing properties of a two-component BEC in spin-dependent optical lattice
Abid Ali; Hiroki Saito
Oral presentation, 日本物理学会第７８回年次大会
16 Sep. 2023 - 粒子数散逸するSpin2 BECの量子多体計算
高橋岳志; 斎藤弘樹
Oral presentation, 日本物理学会第７８回年次大会
16 Sep. 2023 - Long Lifetime Supersolid of Two Component Dipolar BEC
Shaoxiong Li; Hiroki Saito
Oral presentation, 34th IUPAP Conference on Computational Physics CCP2023
06 Aug. 2023 - Supersolid of Two-Component Dipolar Bose-Einstein Condensate
Shaoxiong Li; Uyen Le; Hiroki Saito
Oral presentation, English, 日本物理学会２０２２年秋季大会, Domestic conference
14 Sep. 2022 - Long Lifetime Supersolid of Two Component Dipolar BEC
Shaoxiong Li; Hiroki Saito
Poster presentation, English, 29th International Conference on Low Temperature Physics (LT29), International conference
19 Aug. 2022 - Phase separation and optical multistability of two-component Bose-Einstein condensate in an optical cavity
Abid Ali; Hiroki Saito
Oral presentation, English, 日本物理学会第７７回年次大会, Domestic conference
15 Mar. 2022 - ２成分 BEC 中における障害物ポテンシャル後方での Skyrmion 生 成
坂口京志郎; 神保圭佑; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会第７７回年次大会, Domestic conference
15 Mar. 2022 - ３成分BECにおける界面活性剤的振る舞い
神保圭介; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会2021年秋期大会, オンライン, Domestic conference
20 Sep. 2021 - Orthogonal and antiparallel vortex tubes and energy cascades in quantum turbulence
Tsuyoshi Kadokura; Hiroki Saito
Poster presentation, English, XXXII IUPAP Conference on Computational Physics, Online, International conference
02 Aug. 2021 - 超流動体の乱流状態におけるKolmogorov-Hinze スケール
門倉強; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会第７６回年次大会, Domestic conference
13 Mar. 2021 - 強化学習を用いたボース・アインシュタイン凝縮体の制御
Invited oral presentation, Japanese, ディープラーニングと物理学２０２０オンライン
03 Sep. 2020 - ニューラルネットワークを用いた有限温度系の量子多体状態の計算
入倉直輝; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会 第75回年次大会, Domestic conference
19 Mar. 2020 - ラビ結合した2成分BECにおけるパターン形成
陳特潤; 柴田康介; 衞藤雄二郎; 平野琢也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会 第75回年次大会, Domestic conference
17 Mar. 2020 - Orthogonal and antiparallel vortex tubes and energy cascades in quantum turbulence
Tsuyoshi Kadokura; Hiroki Saito
Poster presentation, English, Turbulence of All Kinds, 大阪市立大学, International conference
08 Jan. 2020 - 機械学習を用いたBose-Hubbard模型の相の分類
山本礼久; 入倉直輝; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１９年秋季大会, Domestic conference
11 Sep. 2019 - 量子乱流における渦度分布の階層構造
門倉強; 斎藤弘樹
Poster presentation, Japanese, 第１６回原子・分子・光科学討論会, Domestic conference
14 Jun. 2019 - スピン１・スピン２BECの混合系における基底状態の相図
入倉直輝; 衞藤雄二郎; 平野琢也; 斎藤弘樹
Poster presentation, Japanese, 第１６回原子・分子・光科学討論会, Domestic conference
14 Jun. 2019 - 複数量子渦輪の不安定性
菅野優美; 幾田麻友美; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会第７４回年次大会, Domestic conference
14 Mar. 2019 - Ground states of Bose-Hubbard model and few-body problems with feedforward neural networks
Hiroki Saito
Invited oral presentation, English, Mini-workshop on "Machine Learning in Physics"
13 Sep. 2018 - スピン1・スピン2BECの混合系における基底状態の相図
入倉直輝; 衞藤雄二郎; 平野琢也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１８年秋季大会, Domestic conference
09 Sep. 2018 - 磁気双極子相互作用するBECにおけるレイリー・テイラー不安定性
Kui-Tian Xi; Tim Byrnes; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１８年秋季大会, Domestic conference
09 Sep. 2018 - 量子乱流における渦度分布の階層構造
門倉強; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１８年秋季大会, Domestic conference
09 Sep. 2018 - Quantum many-body problems and neural networks
Hiroki Saito
Invited oral presentation, English, The 3rd Beijing-Tokyo workshop on ultracold atoms, Invited, 清華大学、北京, International conference
25 Aug. 2018 - Quantum many-body problems and neural networks
斎藤弘樹
Invited oral presentation, Japanese, 深層学習と物理２０１８, Domestic conference
01 Jun. 2018 - ボース・アインシュタイン凝縮体の相分離ダイナミクス光トラップ形状依存性III
柴山均; 鳥居明季; 柴田康介; 高橋雅裕; 衞藤雄二郎; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会 第73回年次大会, 東京理科大学, Domestic conference
24 Mar. 2018 - ラビ結合した２成分ボース・アインシュタイン凝縮体の相分離ダイナミクス
柴田康介; 柴山均; 鳥居明季; 戸田寛之; 鈴木涼太; 高橋雅裕; 衞藤雄二郎; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会 第73回年次大会, 東京理科大学, Domestic conference
24 Mar. 2018 - 機械学習を用いたBose-Hubbard模型の基底状態の計算法
斎藤弘樹; 加藤雅也
Oral presentation, Japanese, 日本物理学会 第73回年次大会, 東京理科大学, Domestic conference
22 Mar. 2018 - Symmetry breaking magnetization in spinor Bose-Einsteini condensates
Hiroki Saito
Invited oral presentation, English, International Symposium on Fluctuation and Structure Out of Equilibrium 2017, Sendai, Japan, International conference
21 Nov. 2017 - Phase separation and pattern formation of binary Bose-Einstein condensates in various optical trap shapes
H. Shibayama; A. Torii; K. Shibata; M. Takahashi; Y. Eto; H. Saito; T. Hirano
Poster presentation, English, International Symposium on Fluctuation and Structure Out of Equilibrium 2017, Sendai, Japan, International conference
21 Nov. 2017 - Phase separation of Rabi-coupled spin states in an 87Rb F=1 BEC
A. Torii; R. Suzuki; H. Toda; H. Shibayama; K. Shibata; M. Takahashi; Y. Eto; H. Saito; T. Hirano
Poster presentation, English, International Symposium on Fluctuation and Structure Out of Equilibrium 2017, Sendai, Japan, International conference
21 Nov. 2017 - Spin sculpting in dissipative spinor Bose-Einstein condensates
Y. Eto; H. Shibayama; A. Torii; H. Saio; T. Hirano
Poster presentation, English, International Symposium on Fluctuation and Structure Out of Equilibrium 2017, Sendai, Japan, International conference
20 Nov. 2017 - ドーナツ型トラップ中におけるスピン軌道相互作用するBEC
Xiao-Fei Zhang; 加藤雅也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１７年秋季大会, Domestic conference
21 Sep. 2017 - スピン軌道相互作用するBECにおける量子渦対
加藤雅也; Xiao-Fei Zhang; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１７年秋季大会, Domestic conference
21 Sep. 2017 - ボース・アインシュタイン凝縮体の相分離ダイナミクス光トラップ形状依存性II
柴山均; 鳥居明季; 柴田康介; 衞藤雄二郎; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会２０１７年秋季大会, Domestic conference
21 Sep. 2017 - Observation of self-organized coherence in dissipative spinor Bose-Einstein condensates
Y. Eto; H. Shibayama; A. Torii; H. Saito; T. Hirano
Oral presentation, English, JSAP-OSA Joint Symposia, 福岡国際会議場, International conference
07 Sep. 2017 - Phase separation of Rabi-coupled spin states in an 87Rb F = 1 BEC
K. Shibata; H. Shibayama; A. Torii; R. Suzuki; H. Toda; Y. Eto; M. Takahashi; H. Saito; T. Hirano
Oral presentation, English, JSAP-OSA Joint Symposia
07 Sep. 2017 - Phase separation dynamics of two-component Bose-Einstein condensates in various optical trap shapes
H. Shibayama; A. Torii; K. Shibata; Y. Eto; H. Saito; T. Hirano
Oral presentation, English, JSAP-OSA Joint Symposia, International conference
07 Sep. 2017 - Matter-wave droplets in a dipolar Bose-Einstein condensate
Hiroki Saito
Invited oral presentation, English, ADVANCES IN MATHEMATICAL MODELLING AND NUMERICAL SIMULATION OF SUPERFLUIDS, Invited, University of Rouen Normandy, Rouen, France, International conference
30 Aug. 2017 - Vortices in spin-orbit coupled Bose-Einstein condensates
Hiroki Saito
Invited oral presentation, English, Mini Vortex Meeting, Invited, 沖縄科学技術大学院大学
05 Jul. 2017 - スピン軌道相互作用するスピノール・ダイポールBECの基底状態
加藤雅也; Xiao-Fei Zhang; 佐々木大地; 斎藤弘樹
Poster presentation, Japanese, 第14会AMO討論会, Domestic conference
30 Jun. 2017 - Self-oscillation in an exciton-polariton condensate
Hiroki Saito
Oral presentation, English, The 4th research area meeting on "Synergy of Fluctuation and Structure", University of Tokyo, Domestic conference
24 Jun. 2017 - Phase separation dynamics of two-component Bose-Einstein condensate in various optical trap shapes
H. Shibayama; A. Torii; K. Shibata; Y. Eto; H. Saito; T. Hirano
Poster presentation, English, The 4th research area meeting on "Synergy of Fluctuation and Structure", University of Tokyo, Domestic conference
23 Jun. 2017 - Spontaneous symmetry breaking in dissipative spinor Bose-Einstein condensates
A. Torii; M. Takahashi; H. Shibayama; Y. Eto; H. Saito; T. Hirano
Poster presentation, English, The 4th research area meeting on "Synergy of Fluctuation and Structure", University of Tokyo, Domestic conference
23 Jun. 2017 - スピン1・スピン2混合ボース凝縮体におけるrephasingの観測
衞藤雄二郎; 柴山均; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会 第７２会年次大会, Domestic conference
19 Mar. 2017 - ボース・アインシュタイン凝縮体相分離ダイナミクスの光トラップ形状依存性
柴山均; 岡田涼太郎; 衞藤雄二郎; 斉藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会 第７２会年次大会, Domestic conference
19 Mar. 2017 - RFスピン制御された87Rbボース・アインシュタイン凝縮体におけるスピン交換衝突
鳥居明季; 鍋田慧太; 高橋雅裕; 柴山均; 衞藤雄二郎; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会 第７２会年次大会, Domestic conference
19 Mar. 2017 - 励起子ポラリトン凝縮体における自励振動と同期
斎藤弘樹; 金本理奈
Oral presentation, Japanese, 日本物理学会 第７２会年次大会, Domestic conference
17 Mar. 2017 - スピン軌道相互作用するスピノール・ダイポールBECの基底状態
加藤雅也; Xiao-Fei Zhang; 佐々木大地; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会 第７２会年次大会, Domestic conference
17 Mar. 2017 - 混和性制御による2成分ボース・アインシュタイン凝縮体の非平衡ダイナミクス
衞藤雄二郎; 高橋雅裕; 國見昌哉; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会２０１６年秋季大会
15 Sep. 2016 - ダイポールBECにおけるドロップレット形成
斎藤弘樹; Kui-Tian Xi
Oral presentation, Japanese, 日本物理学会２０１６年秋季大会
13 Sep. 2016 - Double-quantum spin vortices in SU(3) spin-orbit coupled Bose gases
Xiao-Fei Zhang; Wei Han; Hiroki Saito
Oral presentation, English, 日本物理学会２０１６年秋季大会
13 Sep. 2016 - Twisted spin vortices in a spinor-dipolar Bose-Einstein condensate with Rashba spin-orbit coupling
Masaya Kato; Xiao-Fei Zhang; Daichi Sasaki; Hiroki Saito
Poster presentation, English, Synthetic Topological Quantum Matter, KITPC, Beijing, International conference
01 Aug. 2016 - Self-propulsion and skyrmion dynamics in Bose-Einstein condensates
Hiroki Saito
Oral presentation, English, The 3rd Research Area Meeting of "Synergy of Fluctuation and Structure", Kyushu University
19 Jun. 2016 - Non-Equilibrium dynamics induced by miscible-immiscible transition in binary Bose-Einstein condensates
Y. Eto; M. Takahashi; M. Kunimi; H. Saito; T. Hirano
Poster presentation, English, The 3rd Research Area Meeting of "Synergy of Fluctuation and Structure", Kyushu University
18 Jun. 2016 - Rabi coupling in Bose-Einstein condensates of 87Rb atoms
A. Torii; K. Nabeta; R. Okada; H. Shibayama; M. Takahashi; Y. Eto; H. Saito; T. Hirano
Poster presentation, English, The 3rd Research Area Meeting of "Synergy of Fluctuation and Structure"
18 Jun. 2016 - Magnon Excitations in Spinor Cold Atomic Gases
Masaya Kunimi; Hiroki Saito
Poster presentation, English, CEMS Topical Meeting on Cold Atoms, 理化学研究所
10 Jun. 2016 - Matter-wave droplets in a dipolar BEC of dysprosium
Hiroki Saito
Invited oral presentation, English, The first Beijing-Tokyo workshop on cold atom physics, Invited, Tsinghua Univ., Beijing, China, International conference
13 Apr. 2016 - 励起子ポラリトン超流動体におけるコヒーレント・インコヒーレントポンプを組み合わせた量子渦対生成
金子聡史; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会 第71回年次大会, Domestic conference
20 Mar. 2016 - 87Rbボース・アインシュタイン凝縮体におけるゼーマン準位間のラビ振動
岡田涼太郎; 鍋田慧太; 鳥居明季; 高橋雅裕; 衞藤雄二郎; 國見昌哉; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会第71回年次大会, Domestic conference
19 Mar. 2016 - 超流動体中の物体の自己推進
斎藤弘樹
Oral presentation, Japanese, 日本物理学会第71回年次大会, Domestic conference
19 Mar. 2016 - 二成分BECにおけるSkyrmionの衝突ダイナミクス
金田知也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会第71回年次大会, Domestic conference
19 Mar. 2016 - 量子流体における流体不安定性
斎藤弘樹
Oral presentation, Japanese, 物性研短期研究会「量子乱流と古典乱流の邂逅」
05 Jan. 2016 - 空間構造の転写による２成分ボース・アインシュタイン凝縮体の非平衡ダイナミクス
衛藤雄二郎; 高橋雅裕; 國見昌哉; 斎藤弘樹; 平野琢也
Poster presentation, Japanese, 第９回物性科学領域横断研究会
14 Nov. 2015 - 多成分ボース・アインシュタイン凝縮体の衝突ダイナミクス
鍋田慧太; 衞藤雄二郎; 高橋雅裕; 岡田涼太郎; 國見昌哉; 斎藤弘樹; 平野琢也
Poster presentation, Japanese, 第９回物性科学領域横断研究会
14 Nov. 2015 - 二成分ボース・アインシュタイン凝縮体の多重ドメインによる相対流の抑制
鴇田秀克; 國見昌哉; 衞藤雄二郎; 斎藤弘樹; 平野琢也
Poster presentation, Japanese, 第９回物性科学領域横断研究会
14 Nov. 2015 - スピノールBECのマグノン分散関係に対する磁気双極子相互作用の効果
斎藤弘樹; 國見昌哉
Oral presentation, Japanese, 日本物理学会2015年秋期大会, 関西大学
Sep. 2015 - 強磁性spinorガスにおける1マグノン励起の上限
國見昌哉; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会2015年秋期大会, 関西大学
Sep. 2015 - 多成分ボース・アインシュタイン凝縮体間の衝突と振動の緩和
衞藤雄二郎; 高橋雅裕; 岡田涼太郎; 鍋田慧太; 國見昌哉; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会2015年秋期大会, 関西大学
Sep. 2015 - Magnon Excitations in Spinor Cold Atomic Gases
Masaya Kunimi; Hiroki Saito
Poster presentation, English, The international symposium on Quantum Fluids and Solids QFS2015, Niagara Falls, NY, USA
Aug. 2015 - Collision-induced dynamics in multi-component Bose-Einstein condensates
K. Nabeta; Y. Eto; M. Takahashi; R. Okada; H. Tokita; M. Kunimi; H. Saito; T. Hirano
Poster presentation, English, International Symposium on Fluctuation and Structure out of Equilibrium 2015, 京都, International conference
Aug. 2015 - Suppression of relative current by spin domain formation in immiscible Bose-Einstein condensates
R. Okada; H. Tokita; M. Kunimi; K. Nabeta; Y. Eto; H. Saito; T. Hirano
Poster presentation, English, International Symposium on Fluctuation and Structure out of Equilibrium 2015, International conference
Aug. 2015 - Coherent control and observation of spin dynamics in Bose-Einstein condensates of 87Rb atoms
Y. Eto; H. Saito; T. Hirano
Poster presentation, English, International Symposium on Fluctuation and Structure out of Equilibrium 2015, International conference
Aug. 2015 - Magnon excitations in spinor cold atomic gases
Masaya Kunimi; Hiroki Saito
Poster presentation, English, International Symposium on Fluctuation and Structure out of Equilibrium 2015, 京都, International conference
Aug. 2015 - 冷却原子気体におけるマグノンの分散関係
國見 昌哉; 斎藤 弘樹
Poster presentation, Japanese, ゆらぎと構造の協奏 第2回公開シンポジウム
01 May 2015 - 二成分ボース・アインシュタイン凝縮体におけるスピンドメインの安定性
平野 琢也; 鴇田 秀克; 岡田 涼太郎; 鍋田 慧太; 衛藤 雄二郎; 國見 昌哉; 斎藤 弘樹
Poster presentation, Japanese, ゆらぎと構造の協奏 第2回公開シンポジウム
01 May 2015 - 二成分ボース・アインシュタイン凝縮体におけるスピンドメインの安定性
鴇田; 國見; 岡田; 鍋田; 衛藤; 斎藤; 平野
Oral presentation, Japanese, 日本物理学会第７０会年次大会
22 Mar. 2015 - スピノールBECにおける磁性相間の量子渦対の透過
金田知也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会第７０会年次大会
21 Mar. 2015 - トンネリングによる引力BEC崩壊の量子多体ダイナミクス
斎藤弘樹
Oral presentation, Japanese, 日本物理学会第７０会年次大会
21 Mar. 2015 - Quantum hydrodynamics of ultracold atoms
Hiroki Saito
Oral presentation, English, Second MIPT-UEC Joint Workshop on Optical Science, International conference
Oct. 2014 - スピノールBECの磁気双極子相互作用による空間構造形成
衛藤雄二郎; 斎藤弘樹; 平野琢也
Oral presentation, Japanese, 日本物理学会２０１４年秋季大会, Domestic conference
09 Sep. 2014 - 励起子ポラリトン超流動体における量子渦
斎藤弘樹
Keynote oral presentation, Japanese, 日本物理学会２０１４年秋季大会, Domestic conference
09 Sep. 2014 - 障害物後方への量子渦生成における双安定性
門倉強; 吉田隼; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会２０１４年秋季大会, Domestic conference
08 Sep. 2014 - 励起子ポラリトン超流動体における量子渦の散逸構造
相生智彦; 門倉強; 斎藤弘樹
Poster presentation, Japanese, 「ゆらぎと構造の協奏」第２回領域研究会, Domestic conference
30 Aug. 2014 - Order-disorder oscillations in an exciton-polariton superfluid
Hiroki Saito; Tomohiko Aioi; Tsuyoshi Kadokura
Poster presentation, English, The 7th International Conference on Spontaneous Coherence in Excitonic Systems, Hakone, Japan, International conference
23 Apr. 2014 - スピン２ボース・アインシュタイン凝縮体におけるラーモア歳差運動の測定
長谷川; 富山; 岩出; 鴇田,衛藤; 斎藤,平野
Oral presentation, Japanese, 日本物理学会第６９回年次大会, 東海大学, Domestic conference
28 Mar. 2014 - ポラリトン超流動体における量子渦の散逸構造
相生智彦; 門倉強; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会第６９会年次大会, 東海大学, Domestic conference
27 Mar. 2014 - Hydrodynamic instabilities in Bose-Einstein condensates
Hiroki Saito
Invited oral presentation, English, Workshop on Non-Equilibrium Complex Fluids, Invited, 首都大学東京, International conference
06 Mar. 2014 - ボース・アインシュタイン凝縮体における構造形成
斎藤弘樹
Oral presentation, Japanese, 新学術領域研究「ゆらぎと構造の協奏」第一回研究会
Dec. 2013 - 励起子ポラリトン超流動体におけるパターンの崩壊と復活
斎藤弘樹; 相生智彦; 門倉強
Oral presentation, Japanese, 日本物理学会,２０１３年秋季大会
Sep. 2013 - 磁場勾配中のスピン２ボース・アインシュタイン凝縮体のラーモア歳差運動
衛藤; 長谷川; 富山; 鴇田; 岩出; Sadgrove; 斎藤,平野
Oral presentation, Japanese, 日本物理学会,２０１３年秋季大会
Sep. 2013 - 量子凝縮体
斎藤弘樹
Keynote oral presentation, Japanese, 第１０回原子・分子・光科学討論会, Domestic conference
Jun. 2013 - Quantum hydrodynamics of ultracold atoms
Hiroki Saito
Public symposium, English, UEC-Shanxi Joint Workshop on Optical Science, UEC
Mar. 2013 - 励起子ポラリトン超流動体におけるカルマン渦列
相生智彦; 門倉強; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,第６８回年次大会
Mar. 2013 - 2成分BECにおける回転対称性を破るレイリー・テイラー不安定性
門倉強; 相生智彦; 岸本哲夫; 斎藤弘樹
Public symposium, Japanese, 農工大電通大第９回合同シンポジウム, 電気通信大学 東京農工大学
Dec. 2012 - 原子気体ボース・アインシュタイン凝縮体の流体力学的不安定性
斎藤弘樹
Keynote oral presentation, Japanese, ２０１２年秋季大会, 日本物理学会, Domestic conference
Sep. 2012 - 2成分BEC界面における量子渦対の透過
相生智彦; 門倉強; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,２０１２年秋季大会
Sep. 2012 - スピン2ボース・アインシュタイン凝縮体におけるラーモア歳差運動の測定2
関根佐和子; 富山泰志; 長谷川翔; 池田隼人; 鈴木博祐; Mark Sadgrove; 衛藤雄二郎; 平野琢也; 斉藤弘樹
Oral presentation, Japanese, 日本物理学会,２０１２年秋季大会
Sep. 2012 - Hydrodyanmic instabilities and vortex streets in superfluids
Hiroki Saito
Invited oral presentation, English, IUTAM Symposium "Understanding common aspects of extreme events in fluids", IUTAM, Dublin, International conference
Jul. 2012 - 2成分BECにおける回転対称性を破るレイリー・テイラー不安定性
門倉強; 相生智彦; 佐々木一樹; 岸本哲夫; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会第６７回年次大会
Mar. 2012 - 2成分BECにおけるプラトー・レイリー不安定性
佐々木一樹; 鈴木直也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会第６７回年次大会
Mar. 2012 - Hydrodynamic instabilities in gaseous Bose-Einstein condensates
斎藤弘樹
Invited oral presentation, Japanese, 量子凝縮系におけるdefectsおよびtopology, 物性研短期研究会
Jan. 2012 - レーザー光を用いたボース凝縮体における量子渦対の生成と制御
相生智彦; 門倉強; 岸本哲夫; 斎藤弘樹
Oral presentation, Japanese, レーザー学会,第３２回年次大会
Jan. 2012 - ２成分BECにおける回転位相整合性のブロッキングとダイナミクスの観測に向けて
岸本哲夫; 稲田寛之; 三浦拓朗; 下平崇之; 斎藤弘樹
Oral presentation, Japanese, レーザー学会,第３２回年次大会
Jan. 2012 - 超流動体における量子渦対の生成と制御
相生智彦; 門倉強; 岸本哲夫; 斎藤弘樹
Public symposium, Japanese, 電通大農工大合同シンポジウム, 電通大、農工大
Dec. 2011 - 2成分BECにおける泡の運動
佐々木一樹; 鈴木直也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,２０１１年秋季大会
Sep. 2011 - 様々なポテンシャルによる量子渦対の生成と制御
相生智彦; 門倉強; 岸本哲夫; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,２０１１年秋季大会
Sep. 2011 - 2成分BECにおけるケルビン・ヘルムホルツ不安定性と対向流不安定性のクロスオーバー
鈴木直也; 竹内宏光; 笠松健一; 坪田誠; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,第６６回年次大会
Mar. 2011 - リング型トラップにおける二成分BECの混合性と回転
下平崇之; 岸本哲夫; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,第６６回年次大会
Mar. 2011 - ボース凝縮体における流体不安定性
斎藤弘樹
Invited oral presentation, Japanese, 量子凝縮系の非線形・非平衡現象, 理化学研究所
Jan. 2011 - Various instabilities in Bose-Einstein condensates
Hiroki Saito
Invited oral presentation, English, Model equations in Bose-Einstein Condensation and Related topics, 日本学術振興会日仏共同研究事業SAKURA
Dec. 2010 - ボース・アインシュタイン凝縮体におけるカルマン渦列
佐々木一樹; 鈴木直也; 斎藤弘樹
Oral presentation, Japanese, 農工大電通大合同シンポジウム
Dec. 2010 - ２成分BECにおける回転位相整合性のブロッキングとダイナミクス
三浦拓郎; 稲田寛之; 下平崇之; 斎藤弘樹; 岸本哲夫
Oral presentation, Japanese, 農工大電通大合同シンポジウム
Dec. 2010 - 2成分BECにおける回転位相整合性のブロッキングとダイナミクス
稲田寛之; 三浦拓朗; 下平孝之; 斎藤弘樹; 岸本哲夫
Oral presentation, Japanese, 量子エレクトロニクス研究会
Dec. 2010 - ＢＥＣにおけるカルマン渦列
佐々木一樹; 鈴木直也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,２０１０年秋季大会
Sep. 2010 - Ferrofluidity in dipolar Bose-Einstein condensates
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
Public symposium, English, International Symposium on Physics of New Quantum Phases in Superclean Materials, Yokohama
Mar. 2010 - Interface instabilities in two-component Bose-Einstein condensates
Naoya Suzuki; Kazuki Sasaki; Hiroki Saito
Public symposium, English, International Symposium on Physics of New Quantum Phases in Superclean Materials, Yokohama
Mar. 2010 - ２成分ＢＥＣの界面におけるレイリー・テイラー不安定性
佐々木一樹; 鈴木直也; 赤松大輔; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会第６５回年次大会
Mar. 2010 - 磁気双極子相互作用によるＢＥＣの磁化ダイナミクス
星翔一; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会第６５回年次大会
Mar. 2010 - ２成分ボース・アインシュタイン凝縮体における界面不安定性
鈴木直也; 佐々木一樹; 斎藤弘樹
Public symposium, Japanese, 電通大農工大第６回合同シンポジウム, 電通大、農工大, 東京
Dec. 2009 - 原子気体ＢＥＣにおける磁性流体力学
斎藤弘樹
Keynote oral presentation, Japanese, 日本物理学会, Domestic conference
Sep. 2009 - ２成分ＢＥＣにおけるケルビン・ヘルムホルツ不安定性
鈴木直也; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会
Sep. 2009 - スピノールＢＥＣにおける動的カシミール効果
斎藤弘樹; 日向裕幸
Oral presentation, Japanese, 日本物理学会,日本物理学会６４回年次大会
2009 - Interface instabilities in two-component Bose-Einstein condensates
鈴木直也; 佐々木一樹; 斎藤弘樹
Public symposium, Japanese, スーパークリーン物質で実現する新しい量子相の物理 A03,A04合同研究会, 箱根
2009 - ダイポールＢＥＣにおける磁区パターン形成
川口由紀; 斎藤弘樹; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会第６４回年次大会
2009 - Ferrofluidity in dipolar Bose-Einstein condensates
斎藤弘樹
Oral presentation, Japanese, 特定領域研究,スーパークリーン物質で実現する新しい量子相の物理A03,A04合同研究会
2009 - Topological defect formation in spinor and dipolar Bose-Einstein condensates
Hiroki Saito
Invited oral presentation, English, The 8th Asian International Seminar on Atomic and Molecular Physics, Perth, Australia, International conference
2008 - Bose-Einstein condensates of atomic gases: recent topics
Hiroki Saito
Invited oral presentation, English, オイラー方程式の数理, Kyoto University
2008 - Kibble-Zurek mechanism in magnetization of a spinor Bose-Einstein condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
Public symposium, English, The 9th International Symposium on Foundations of Quantum Mechanics in the Light of New Technology, Hitachi Laboratory, Saitama
2008 - ラビ振動によるＢＥＣドロップレットの安定化
斎藤弘樹; R. G. Hulet; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会秋季大会
2008 - 回転トラップ中のＢＥＣにおけるスピン渦の生成
千葉宏樹; 斎藤弘樹
Public symposium, Japanese, 電通大農工大第５回合同シンポジウム, 東京
2008 - スピノールＢＥＣにおけるhalf-quantum vortexの磁化ダイナミクス
星翔一; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会秋季大会
2008 - スピノールＢＥＣにおける1/2量子渦の磁化ダイナミクス
星翔一; 斎藤弘樹
Public symposium, Japanese, 電通大農工大第５回合同シンポジウム, 東京
2008 - Kibble-Zurek mechanism in a spinor Bose-Einstein condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
Public symposium, English, International Symposium on Coherent Optical Science, UEC, Tokyo, International conference
2007 - 境界条件を課さない動的カシミール効果
斎藤弘樹; 日向裕幸
Invited oral presentation, Japanese, 静的および動的カシミール効果, 立命館大学
2007 - Kibble-Zurek mechanism in magnetization of a spinor Bose-Einstein condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
Public symposium, English, International Symposium on Physics of New Quantum Phase in Superclean Materials, 岐阜
2007 - Kibble-Zurek mechanism in a spinor Bose-Einstein condensate
Hiroki Saito; Yuki Kawaguchi; Masahito Ueda
Public symposium, English, International Symposium on Coherent Optical Science, UEC, Tokyo
2007 - フィードバック制御によるＢＥＣドロップレットの安定化
斎藤弘樹; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会２００７春季大会
2007 - スピノールＢＥＣの自発磁化過程
斎藤弘樹; 川口由紀; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会６２回年次大会
2007 - スピノールＢＥＣのダイナミクスにおける量子揺らぎの効果
千葉宏樹; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会６２回年次大会
2007 - スピノールＢＥＣのダイナミクスにおける量子揺らぎの効果
千葉宏樹; 斎藤弘樹
Oral presentation, Japanese, 日本物理学会,日本物理学会６２回年次大会, 東京
2007 - 磁場中のスピノルＢＥＣにおけるダイポール相互作用
川口由紀; 斎藤弘樹; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会第６２回年次大会
2007 - ダイポールＢＥＣの基底状態における自発循環
川口由紀; 斎藤弘樹; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会２００７年春季大会
2007 - Kibble-Zurek mechanism in magnetization of a spinor BEC
斎藤弘樹; 川口由紀; 上田正仁
Oral presentation, Japanese, 特定領域研究,スーパークリーン物質で実現する新しい量子相の物理A03,A04合同研究会
2007 - Symmetry breaking in scalar, spinor, and rotating Bose-Einstein condensates
Hiroki Saito
Invited oral presentation, English, 18th International IUPAP Conference on Few-Body Problems in Physics, IUPAP, Santos, Brazil, International conference
2006 - スピン２ＢＥＣのダイナミクスから磁性相を決定する方法
斎藤弘樹; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会６１回年次大会
2006 - スピノールＢＥＣにおける自発的渦形成
斎藤弘樹; 川口由紀; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会２００６年秋季大会
2006 - ダイポールＢＥＣにおけるアインシュタイン・ドハース効果
川口由紀; 斎藤弘樹; 上田正仁
Oral presentation, Japanese, 日本物理学会,日本物理学会２００６年秋季大会
2006
Courses
- 上級コンピュータ演習
Apr. 2020 - Present
電気通信大学 - 基礎電磁気学および演習
Apr. 2017 - Present
The University of Electro-Communications - 量子力学第一
Apr. 2012 - Present
電気通信大学 - 凝縮体量子工学特論
Apr. 2006 - Present
電気通信大学 - 量子力学
Apr. 2011 - Mar. 2024
The University of Electro-Communications - 上級コンピュータ演習
The University of Electro-Communications - K課程輪講
The University of Electro-Communications - K課程輪講
電気通信大学 - 量子力学
電気通信大学 - UECパスポートセミナー
The University of Electro-Communications - UECパスポートセミナー
電気通信大学 - 電磁気学および演習
The University of Electro-Communications - 電磁気学および演習
電気通信大学 - 量子力学
The University of Electro-Communications - 凝縮体量子工学特論
The University of Electro-Communications - 基礎電磁気学および演習
電気通信大学 - 大学院技術英語
The University of Electro-Communications - 基礎電磁気学および演習
The University of Electro-Communications - 凝縮体量子工学特論
The University of Electro-Communications - 凝縮体量子工学特論
電気通信大学 - 大学院技術英語
The University of Electro-Communications - 大学院技術英語
電気通信大学 - コンピュータ演習
The University of Electro-Communications - コンピュータ演習
電気通信大学 - 基盤理工学専攻基礎
The University of Electro-Communications - 基盤理工学専攻基礎
電気通信大学 - 量子力学第一
The University of Electro-Communications - 量子力学第一
The University of Electro-Communications - 量子力学第一
電気通信大学
Research Themes
- 深層ニューラルネットワークを駆使した冷却原子系における量子多体計算手法の開拓
2020 - 2022 - 磁性超流体における自己束縛した量子小滴
01 Apr. 2017 - 31 Mar. 2020 - 光格子変調による原子波束の選択的量子操作
2017 - 2019 - 協同現象を利用した振動子集団の制御理論
2016 - 2018 - ポラリトン超流動体における量子散逸構造
2014 - 2016 - Study on superfluidity of atomic gases with internal degrees of freedom.
UEDA Masahito; HIRANO Takuya; SAITO Hiroki; KUWAMOTO Takeshi; TOJO Satoshi; KAWAGUCHI Yuki; TOJO Satoshi; KAWAGUCHI Yuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research on Priority Areas, We studies superfluid properties of Bose-Einstein condensates (BECs) with internal degrees of freedom. We have numerically demonstrated that by changing an external magnetic field spin vortices are spontaneously generated. This provides an atomic-gas demonstration of the Kibble-Zurek mechanism. We have also demonstrated that exotic topological excitations such as knots and non-Abelian vortices can be created in spinor BECs., 17071005
2005 - 2009 - Theoretical study on the Quantum Statistical Aspects of BEC
UEDA Masahito; ADACHI Satoshi; MACHIDA Kazushige; OHMI Tetsuo; SAITO Hiroki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research on Priority Areas, The A4 group consisted of theoreticians working on the physics of BEC. (1) Ueda's group studied on the physics of BEC under attractive interaction. The state of the attractive BEC is at best a metastable state and eventually collapses. They studied the mechanism of the BEC collapsing and found that a BEC near the critical temperature grows macroscopic quantum tunneling, and then the BEC collapses. The found also the quantization of circulation that was guaranteed in a repulsive BEC was only partially satisfied in an attractive BEC. The quantization of circulation is know as a signature of superfluidity. The breakdown of the quantization in an attractive BEC adds new insight on the fundamental properties of BEC. They studied also the dynamics of BEC when the interaction is switched from repulsive to attractive. Their findings are (i) when a large BEC is switched from repulsive to attractive interaction, various nonlinear pattern (shell structure, layered structure,....) is expected to appear. (ii) They studied the dynamics of vortex generated when the interaction is repulsive. They found various dynamical instabilities that was a function of the interaction strength. The instabilities cause fracture of the vortex, and the vortex collapses. (iii) They showed in an attractive BEC two-dimensional bright is stabilized if the sign and amplitude of the interaction potential is modulated. Ohmi and Machida studied on me phase separation of multi-state BEC, dynamics of the phase transition, a new method of generating vortices, and on the stability of vortices., 11216204
1999 - 2002
