Bulletin of the American Physical Society
48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017; Sacramento, California
Session P5: Spinor Gases |
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Chair: Rudolf Grimm, IQOQI Innsbruck Room: 310 |
Thursday, June 8, 2017 2:00PM - 2:12PM |
P5.00001: Quench dynamics of a spinor condensate with strong spin-dependent interactions Hil F H Cheung, Yogesh S Patil, Mukund Vengalattore Spinor condensates exhibit a rich phase diagram of magnetically ordered phases arising from the interplay between spin-dependent interactions and superfluidity. The spinor condensates studied to date ($^{\mathrm{87}}$Rb and $^{\mathrm{23}}$Na) exhibit weak spin-dependent interactions with little coupling between the spin (magnon) excitations and the mass (phonon) excitations. In contrast, the F$=$1 spinor condensates of $^{\mathrm{7}}$Li exhibit commensurate strengths of spin-dependent and spin-independent interactions, leading to qualitative changes in the equilibrium phases and spinor dynamics. We describe the quench dynamics of a $^{\mathrm{7}}$Li spinor gas between a spin nematic and ferromagnetic phase, discuss the emergent ferromagnetic spin texture and topological defects in accordance with the Kibble-Zurek mechanism and contrast this behavior with that observed in weakly interacting spinor condensates such as $^{\mathrm{87}}$Rb. [Preview Abstract] |
Thursday, June 8, 2017 2:12PM - 2:24PM |
P5.00002: Quantum Interferometry with Microwave-dressed F=1 Spinor Bose-Einstein Condensates: Role of Initial States and Long Time Evolution Qimin Zhang, Arne Schwettmann, Eite Tiesinga We numerically investigate atom interferometry based on spin-exchange collisions in $F=1$ spinor Bose-Einstein condensates in the regime where both the truncated Wigner and the Bogoliubov approximations break down. The interferometer promises to beat the shot-noise limit even in the case of large atom-number population in the arms of the interferometer. Spin-exchange collisions in $F=1$ spinor Bose-Einstein condensates, where two atoms with magnetic quantum number $m_F=0$ collide and change into a pair with $m_F=\pm1$, are useful to implement matter-wave quantum optics in spin space, such as quantum-enhanced interferometry, because the collisions generate entanglement and they can be precisely controlled using microwave dressing. Here, we show numerically that the sensitivity of spin-mixing interferometry can be enhanced to go beyond the shot-noise limit even with a large population of $m_F=\pm 1$ states, $1\ll N_{m_F=\pm1}\ll N$, and after long evolution times. This is done by using classically seeded initial states with a small initial population in the $m_F=\pm1$ states and using long evolution times $t\gg h/c$, where c is the spin-dependent interaction energy. [Preview Abstract] |
Thursday, June 8, 2017 2:24PM - 2:36PM |
P5.00003: Efficient production of spin singlets in lattice-confined spinor condensates Lichao Zhao, Zihe Chen, Tao Tang, Yingmei Liu We present an efficient experimental scheme for a production of spin singlets in an antiferromagnetic spinor condensate confined by a cubic optical lattice. Via two independent detection methods, we demonstrate that about 80 percent of atoms in the lattice-confined spinor condensate can form spin singlets, immediately after the atoms cross a first-order superfluid to Mott-insulator phase transition in a sufficiently low microwave dressing field. We also discuss a good agreement between our data and the mean field theory, and two applications of spin singlets in quantum information science. [Preview Abstract] |
Thursday, June 8, 2017 2:36PM - 2:48PM |
P5.00004: Precise measurements on a quantum phase transition in antiferromagnetic spinor Bose-Einstein condensates Chandra Raman, Anshuman Vinit We have experimentally investigated the quench dynamics of antiferromagnetic spinor Bose-Einstein condensates in the vicinity of a zero temperature quantum phase transition at zero quadratic Zeeman shift $q$. A key feature of this work was removal of magnetic field inhomogeneities, resulting in a steep change in behavior near the transition point. The quadratic Zeeman shift at the transition point was resolved to 250 mHz uncertainty, equivalent to an energy resolution of $k_B \times 12$ picoKelvin. To our knowledge, this is the first demonstration of sub-Hz precision measurement of a phase transition in quantum gases. It paves the way toward observing shifts of the transition point due to finite particle number $N$ that scale as $1/N$, and also, to potential Heisenberg limited spectroscopy with antiferromagnetic spinor gases. [Preview Abstract] |
Thursday, June 8, 2017 2:48PM - 3:00PM |
P5.00005: Coarsening in the one-dimensional spin-1 spinor Bose-Hubbard model Kazuya Fujimoto, Ryusuke Hamazaki, Masahito Ueda A Spinor gas has a rich variety of phases, being a suitable system to investigate coarsening in an isolated quantum system. Most recent works for the coarsening in ultra-clod atomic gases focus on two-dimensional systems and find domain-growth laws characteristic of the classical binary liquid [1,2]. Under such a background, we theoretically study the coarsening in the one-dimensional spin-1 spinor Bose-Hubbard model. In terms of the coarsening, this system is essentially different from the previous ones because, in the one-dimensional system, the domain wall does not have the curvature and cannot move by itself. This leads to an expectation that the one-dimensional coarsening belongs to a universality class different from the binary liquid. To reveal this class, we have focused on a deep superfluid regime in our model, and analytically shown that the domain-growth law is characterized by the exponential integral not seen in the binary liquid. Furthermore, we have numerically confirmed this growth law by using the truncated Wigner approximation. \\ \\ $1^$ K. Kudo and Y. Kawaguchi, Phys. Rev. A {\bf 88}, 013630 (2013). \\ $2^$ L. Williamson and P.B. Blakie, Phys. Rev. Lett. {\bf 116}, 025301 (2016). [Preview Abstract] |
Thursday, June 8, 2017 3:00PM - 3:12PM |
P5.00006: Efficient generation of many-body singlet states of spin-1 bosons Wenxian Zhang, Huanying Sun, Peng Xu, Han Pu A quantum many-body spin singlet state is theoretically predicted as the ground state of an antiferromagnetically interacting spin-1 bosons at zero magnetic field. This fragile state would be broken even in a tiny magnetic field of microGauss. We develop an efficient stepwise adiabatic merging (SAM) method to generate many-body singlet states in antiferromagnetic spin-1 bosons in optical lattices with double-well arrays, by adiabatically ramping up the double-well bias. With an appropriate choice of bias sweeping rate, the SAM protocol predicts a fidelity as high as 90\% for a sixteen-body singlet state and even higher fidelities for smaller even-body singlet states in a magnetic field of a few tens milliGausses. During their evolution, the spin-1 bosons exhibit wonderful squeezing dynamics, manifested by odd-even oscillations of the experimental observable of generalized squeezing parameter. The generated many-body singlet states may find practical applications in precision measurement of magnetic field gradient. [Preview Abstract] |
Thursday, June 8, 2017 3:12PM - 3:24PM |
P5.00007: Spin-incoherent Luttinger liquid of one-dimensional spin-1 Bose gas Hsiang-Hua Jen, Sungkit Yip A plethora of studies on one-dimensional (1D) quantum systems involve their ground state properties such as spatial and momentum distributions, quantum magnetism in a spinor Bose gas, and low-energy excitations in the Luttinger liquid model. A spinful quantum system in the spin-incoherent regime also provides a new avenue for studying 1D quantum many-body systems. Spin-incoherent Luttinger liquid (SILL) forms a different universality class from the Luttinger liquid, where the temperature is large enough that the degenerate spin configurations emerge while low enough that charge excitation is forbidden. In the SILL regime of a 1D spin-1 Bose gas, we investigate its many-body properties in Tonks-Girardeau limit in a harmonic trap. With zero magnetic field in the sector of $S_z=0$, we derive the density matrix for the three individual components of the spin-1 Bose gas(spin-up,down,and 0). The momentum distributions are broadened compared with the spinless Bose gas and in the large momentum limit follow the asymptotic $1/p^4$ dependence but with reduced coefficients. While the density matrices and momentum distributions differ between different spin components for small N, at large N they approach each other. We show these by analytic arguments and numerical calculations up to N=16. [Preview Abstract] |
Thursday, June 8, 2017 3:24PM - 3:36PM |
P5.00008: Internal structure of vortices in a dipolar spinor Bose-Einstein condensate Magnus O. Borgh, Justin Lovegrove, Janne Ruostekoski We demonstrate how dipolar interactions (DI) can have pronounced effects on the structure of vortices in atomic spinor Bose-Einstein condensates and illustrate generic physical principles that apply across dipolar spinor systems. We then find and analyze the cores of singular non-Abelian vortices in a spin-3 $^{52}$Cr condensate. Using a simpler spin-1 model system, we analyze the underlying dipolar physics and show how a dipolar healing length interacts with the hierarchy of healing lengths of the contact interaction and leads to simple criteria for the core structure: vortex core size is restricted to the shorter spin-dependent healing length when the interactions both favor the ground-state spin condition, but can conversely be enlarged by DI when interactions compete. We further demonstrate manifestations of spin-ordering induced by the DI anisotropy, including DI-dependent angular momentum of nonsingular vortices, as a result of competition with adaptation to rotation, and potentially observable internal vortex-core spin textures. [Preview Abstract] |
Thursday, June 8, 2017 3:36PM - 3:48PM |
P5.00009: Chiral spin condensation in a double-valley optical lattice Xiaopeng Li, Yinghai Wu We study a spinor (two component) Bose gas confined in a one dimensional double-valley optical lattice which has a double-well structure in momentum space. With field theory analysis we find that the spinor bosons in the double-valley band generically form a spin-charge mixed chiral spin quasi-condensate. We further perform exact numeric calculations for a concrete $\pi$-flux triangular ladder system, where we confirm the robustness of the chiral spin order against interactions and quantum fluctuations. This exotic atomic Bose condensate exhibits spatially staggered spin loop currents without any charge dynamics despite the complete absence of spin-orbit coupling in the system, paving a novel venue to atom-spintronics. By calculating entanglement entropy scaling and conformal-field-theory central charge, we establish that the low energy effective theory for the chiral spin condensate is a two-component Luttinger liquid. Our predictions are readily detectable in atomic experiments through spin resolved time-of-flight techniques. [Preview Abstract] |
Thursday, June 8, 2017 3:48PM - 4:00PM |
P5.00010: Non-Abelian Geometric Phases Carried by the Quantum Noise Matrix Bharath H. M., Matthew Boguslawski, Maryrose Barrios, Michael Chapman Topological phases of matter are characterized by topological order parameters that are built using Berry’s geometric phase. Berry’s phase is the geometric information stored in the overall phase of a quantum state. We show that geometric information is also stored in the second and higher order spin moments of a quantum spin system, captured by a non-abelian geometric phase. The quantum state of a spin-S system is uniquely characterized by its spin moments up to order 2S. The first-order spin moment is the spin vector, and the second-order spin moment represents the spin fluctuation tensor, i.e., the quantum noise matrix. When the spin vector is transported along a loop in the Bloch ball, we show that the quantum noise matrix picks up a geometric phase. Considering spin-1 systems, we formulate this geometric phase as an SO(3) operator. Geometric phases are usually interpreted in terms of the solid angle subtended by the loop at the center. However, solid angles are not well defined for loops that pass through the center. Here, we introduce a generalized solid angle which is well defined for all loops inside the Bloch ball, in terms of which, we interpret the SO(3) geometric phase. This geometric phase can be used to characterize topological spin textures in cold atomic clouds. [Preview Abstract] |
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