%0 Journal Article
%J Physical Review Letters
%D 2012
%T Topological Flat Bands from Dipolar Spin Systems
%A Norman Y. Yao
%A Chris R. Laumann
%A Alexey V. Gorshkov
%A Steven D. Bennett
%A Eugene Demler
%A Peter Zoller
%A Mikhail D. Lukin
%X We propose and analyze a physical system that naturally admits two-dimensional topological nearly flat bands. Our approach utilizes an array of three-level dipoles (effective S = 1 spins) driven by inhomogeneous electromagnetic fields. The dipolar interactions produce arbitrary uniform background gauge fields for an effective collection of conserved hardcore bosons, namely, the dressed spin-flips. These gauge fields result in topological band structures, whose bandgap can be larger than the corresponding bandwidth. Exact diagonalization of the full interacting Hamiltonian at half-filling reveals the existence of superfluid, crystalline, and supersolid phases. An experimental realization using either ultra-cold polar molecules or spins in the solid state is considered.
%B Physical Review Letters
%V 109
%8 2012/12/26
%G eng
%U http://arxiv.org/abs/1207.4479v3
%N 26
%! Phys. Rev. Lett.
%R 10.1103/PhysRevLett.109.266804
%0 Journal Article
%J Physical Review A
%D 2011
%T Quantum Magnetism with Polar Alkali Dimers
%A Alexey V. Gorshkov
%A Salvatore R. Manmana
%A Gang Chen
%A Eugene Demler
%A Mikhail D. Lukin
%A Ana Maria Rey
%X We show that dipolar interactions between ultracold polar alkali dimers in optical lattices can be used to realize a highly tunable generalization of the t-J model, which we refer to as the t-J-V-W model. The model features long-range spin-spin interactions J_z and J_perp of XXZ type, long-range density-density interaction V, and long-range density-spin interaction W, all of which can be controlled in both magnitude and sign independently of each other and of the tunneling t. The "spin" is encoded in the rotational degree of freedom of the molecules, while the interactions are controlled by applied static electric and continuous-wave microwave fields. Furthermore, we show that nuclear spins of the molecules can be used to implement an additional (orbital) degree of freedom that is coupled to the original rotational degree of freedom in a tunable way. The presented system is expected to exhibit exotic physics and to provide insights into strongly correlated phenomena in condensed matter systems. Realistic experimental imperfections are discussed.
%B Physical Review A
%V 84
%8 2011/9/15
%G eng
%U http://arxiv.org/abs/1106.1655v1
%N 3
%! Phys. Rev. A
%R 10.1103/PhysRevA.84.033619
%0 Journal Article
%J Physical Review Letters
%D 2011
%T Tunable Superfluidity and Quantum Magnetism with Ultracold Polar Molecules
%A Alexey V. Gorshkov
%A Salvatore R. Manmana
%A Gang Chen
%A Jun Ye
%A Eugene Demler
%A Mikhail D. Lukin
%A Ana Maria Rey
%X By selecting two dressed rotational states of ultracold polar molecules in an optical lattice, we obtain a highly tunable generalization of the t-J model, which we refer to as the t-J-V-W model. In addition to XXZ spin exchange, the model features density-density interactions and novel density-spin interactions; all interactions are dipolar. We show that full control of all interaction parameters in both magnitude and sign can be achieved independently of each other and of the tunneling. As a first step towards demonstrating the potential of the system, we apply the density matrix renormalization group method (DMRG) to obtain the 1D phase diagram of the simplest experimentally realizable case. Specifically, we show that the tunability and the long-range nature of the interactions in the t-J-V-W model enable enhanced superfluidity. Finally, we show that Bloch oscillations in a tilted lattice can be used to probe the phase diagram experimentally.
%B Physical Review Letters
%V 107
%8 2011/9/8
%G eng
%U http://arxiv.org/abs/1106.1644v1
%N 11
%! Phys. Rev. Lett.
%R 10.1103/PhysRevLett.107.115301
%0 Journal Article
%J Physical Review A
%D 2010
%T Adiabatic preparation of many-body states in optical lattices
%A Anders S. Sorensen
%A Ehud Altman
%A Michael Gullans
%A J. V. Porto
%A Mikhail D. Lukin
%A Eugene Demler
%X We analyze a technique for the preparation of low entropy many body states of atoms in optical lattices based on adiabatic passage. In particular, we show that this method allows preparation of strongly correlated states as stable highest energy states of Hamiltonians that have trivial ground states. As an example, we analyze the generation of antiferromagnetically ordered states by adiabatic change of a staggered field acting on the spins of bosonic atoms with ferromagnetic interactions.
%B Physical Review A
%V 81
%8 2010/6/22
%G eng
%U http://arxiv.org/abs/0906.2567v3
%N 6
%! Phys. Rev. A
%R 10.1103/PhysRevA.81.061603
%0 Journal Article
%J Physical Review Letters
%D 2010
%T Photonic Phase Gate via an Exchange of Fermionic Spin Waves in a Spin Chain
%A Alexey V. Gorshkov
%A Johannes Otterbach
%A Eugene Demler
%A Michael Fleischhauer
%A Mikhail D. Lukin
%X We propose a new protocol for implementing the two-qubit photonic phase gate. In our approach, the pi phase is acquired by mapping two single photons into atomic excitations with fermionic character and exchanging their positions. The fermionic excitations are realized as spin waves in a spin chain, while photon storage techniques provide the interface between the photons and the spin waves. Possible imperfections and experimental systems suitable for implementing the gate are discussed.
%B Physical Review Letters
%V 105
%8 2010/8/5
%G eng
%U http://arxiv.org/abs/1001.0968v3
%N 6
%! Phys. Rev. Lett.
%R 10.1103/PhysRevLett.105.060502
%0 Journal Article
%J Nature Physics
%D 2008
%T Anyonic interferometry and protected memories in atomic spin lattices
%A Liang Jiang
%A Gavin K. Brennen
%A Alexey V. Gorshkov
%A Klemens Hammerer
%A Mohammad Hafezi
%A Eugene Demler
%A Mikhail D. Lukin
%A Peter Zoller
%X Strongly correlated quantum systems can exhibit exotic behavior called topological order which is characterized by non-local correlations that depend on the system topology. Such systems can exhibit remarkable phenomena such as quasi-particles with anyonic statistics and have been proposed as candidates for naturally fault-tolerant quantum computation. Despite these remarkable properties, anyons have never been observed in nature directly. Here we describe how to unambiguously detect and characterize such states in recently proposed spin lattice realizations using ultra-cold atoms or molecules trapped in an optical lattice. We propose an experimentally feasible technique to access non-local degrees of freedom by performing global operations on trapped spins mediated by an optical cavity mode. We show how to reliably read and write topologically protected quantum memory using an atomic or photonic qubit. Furthermore, our technique can be used to probe statistics and dynamics of anyonic excitations.
%B Nature Physics
%V 4
%P 482 - 488
%8 2008/4/20
%G eng
%U http://arxiv.org/abs/0711.1365v1
%N 6
%! Nat Phys
%R 10.1038/nphys943