Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session T1: Quantum Magnetism and Frustration in AMO Systems |
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Chair: Ana Maria Rey, JILA Room: 200A |
Friday, June 7, 2013 8:00AM - 8:30AM |
T1.00001: Topological phases in polar-molecule quantum magnets Invited Speaker: Alexey Gorshkov We will show that ultracold polar molecules pinned in an optical lattice and interacting via dipolar interactions can be used to implement a huge variety of exotic quantum magnets. These can be used to realize, for example, fractional Chern insulators, symmetry protected topological phases, the bilinear-biquadratic spin-1 Hamiltonian, and the Kitaev honeycomb model. [References: PRL 109, 266804 (2012), PRB 87, 081106(R) (2013), arXiv:1212.4839 (PRL in press), arXiv:1301.5636] [Preview Abstract] |
Friday, June 7, 2013 8:30AM - 9:00AM |
T1.00002: Towards Simulating the Transverse Ising Model in a 2D Array of Trapped Ions Invited Speaker: Brian Sawyer Two-dimensional Coulomb crystals provide a useful platform for large-scale quantum simulation. Penning traps enable confinement of large numbers of ions ($>$100) and allow for the tunable-range spin-spin interactions demonstrated in linear ion strings [1], facilitating simulation of quantum magnetism at a scale that is currently intractable on classical computers. We readily confine hundreds of Doppler laser-cooled $^9$Be$^+$ within a Penning trap, producing a planar array of ions with self-assembled triangular order. The transverse ``drumhead'' modes of our 2D crystal along with the valence electron spin of Be$^+$ serve as a resource for generating spin-motion and spin-spin entanglement. Applying a spin-dependent optical dipole force (ODF) to the ion array, we perform spectroscopy and thermometry of individual drumhead modes [2]. This ODF also allows us to engineer long-range Ising spin couplings of either ferromagnetic or anti-ferromagnetic character whose approximate power-law scaling with inter-ion distance, $d$, may be varied continuously from $1/d^0$ to $1/d^3$ [3]. An effective transverse magnetic field is applied via microwave radiation at the $\sim$124-GHz spin-flip frequency, and ground states of the effective Ising Hamiltonian may in principle be prepared adiabatically by slowly decreasing this transverse field in the presence of the induced Ising coupling. Long-range anti-ferromagnetic interactions are of particular interest due to their inherent spin frustration and resulting large, near-degenerate manifold of ground states.\\[4pt] [1] R. Islam et al., Nat. Commun. \textbf{2}, 377 (2011).\\[0pt] [2] B. C. Sawyer et al., Phys. Rev. Lett. \textbf{108}, 213003 (2012).\\[0pt] [3] J. W. Britton et al., Nature \textbf{404}, 489 (2012). [Preview Abstract] |
Friday, June 7, 2013 9:00AM - 9:30AM |
T1.00003: Frustration in spin models with cavity-mediated interactions Invited Speaker: Sarang Gopalakrishnan Ultracold atoms confined in transversely pumped optical cavities experience cavity-mediated interactions, which can give rise to phenomena such as crystallization [1] that are otherwise difficult to realize using ultracold atoms. We show that for atoms with three or more internal levels, the spin-dependent cavity-mediated interactions are long-ranged and sign-changing, like the RKKY interaction; therefore, ensembles of such atoms subject to frozen-in positional randomness can realize spin systems having disordered and frustrated interactions [2]. We map the problem of spins with cavity-mediated interactions onto a variant of the Hopfield associative-memory model. Using this mapping we argue that if the spins are coupled to sufficiently many cavity modes, the cavity-mediated interactions give rise to a spin glass. We then discuss how spins in cavities can emulate models of interacting bosons subject to purely ``off-diagonal'' disorder, which exhibit Mott glass and random-singlet glass phases [3] (hitherto unrealized using ultracold atoms). We discuss how the realizable glassy phases can be detected through their slow dynamics, as well as their imprint on the correlations of the light emitted from the cavity. Finally, we discuss the robustness of the predicted glassy physics in the presence of driving and dissipation. \\[4pt] [1] P. Domokos and H. Ritsch, Phys. Rev. Lett. 89, 253003 (2002); S. Gopalakrishnan, B.L. Lev, and P.M. Goldbart, Nature Physics 5, 845 (2009); K. Baumann et al., Nature 464, 1301 (2010). \\[0pt] [2] S. Gopalakrishnan, B.L. Lev, and P.M. Goldbart, Phys. Rev. Lett. 107, 277201 (2011).\\[0pt] [3] J. J. Hopfield, PNAS 79, 2554 (1982). [Preview Abstract] |
Friday, June 7, 2013 9:30AM - 10:00AM |
T1.00004: Quantum Simulation of Frustrated Magnetism with Many Trapped Ions Invited Speaker: Crystal Senko A collection of trapped atomic ions is an excellent system for simulating quantum many-body physics, like magnetism, which may be difficult to access via classical computation or traditional condensed-matter experiments. Our large crystals of 10-20 ions comprise a platform to study a long-range quantum Ising model with tunable couplings in a 1D spin chain. State-dependent optical dipole forces exploit the Coulomb interaction to generate the spin-spin couplings, and fluorescence measurements on a camera are used to read out individual spin states. We investigated the spin order resulting from changing the range of antiferromagnetic interactions or the strength of an axial magnetic field, demonstrating our control over the amount of frustration present. We are turning to the study of dynamics in this system, with the aim of exploring topics including adiabaticity, spectroscopy of the Hamiltonian, the emergence of Kibble-Zurek-like behavior in a finite system, thermalization in an isolated quantum system, and nonequilibrium phase transitions. There is great promise in extending the system to 30+ spins, where computations become classically intractable. Co-authors are R. Islam, P. Richerme, W. C. Campbell, S. Korenblit, J. Smith, A. Lee, E. E. Edwards, C.-C. J. Wang, J. K. Freericks, and C. Monroe. [Preview Abstract] |
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