Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session J40: Quantum Simulation II |
Hide Abstracts |
Sponsoring Units: DAMOP Chair: Khan W. Mahmud, University of Maryland Room: 349 |
Tuesday, March 19, 2013 2:30PM - 2:42PM |
J40.00001: Simulation of a Non-Equilibrium Localization Transition of Photons in a Superconducting Circuit-QED Dimer Darius Sadri, James Raftery, Andrew Houck, Hakan Tureci, Sebastian Schmidt, Devin Underwood, Will Shanks, Srikanth Srinivasan, Mikola Bordyuh The exponential scaling of Hilbert space dimension with number of quantum degrees of freedom, while serving as a resource for quantum computation, makes simulation of large quantum systems on classical computers prohibitive, particularly when interactions with an environment are included. Quantum simulation promises to make possible the investigation of rich quantum behavior on a controlled quantum mechanical device (effectively a specialized quantum computer), deepening our understanding of fascinating physics such as quantum phase transitions, non-equilibrium quantum dynamics, and quantum chaos. Superconducting circuit Quantum Electrodynamics (cQED) is a promising framework for the realization of such simulators. As a first step, we have constructed a quantum simulator for a conjectured dissipation-driven localization transition of light in a dimer using cQED techniques. A proper understanding of the physics and signature of this transition has been made possible by our development of a new classical simulator based on the stochastic quantum jump method, taking advantage of a fractal structure in our Hamiltonian to enable a study of the very large Hilbert spaces demanded by this problem. We present results of these simulations, and discuss possible future directions. [Preview Abstract] |
Tuesday, March 19, 2013 2:42PM - 2:54PM |
J40.00002: Quantum simulations of cooper pairing and driven nonlinear Schr\"{o}dinger equation with stationary light Priyam Das, Mingxia Huo, Changsuk Noh, B. M. Rodriguez-Lara, Dimitris G. Angelakis Strongly correlated states of photons generated in strongly coupled light-matter interfaces, such optical waveguides interacting with ensembles of cold atoms, have recently emerged as promising routes for a new kind of quantum simulators. In this work, we present two of our most recent results along this line, motivated by earlier proposals on strongly interacting stationary polaritons and a proposal to create an effective polaritonic lattice potential. In the first part, we show how to realize an optically tunable two-component Bose-Hubbard model and discuss the feasibility of generating an effective Fermi-Hubbard model of polaritons. This allows one to simulate and detect the 1D analog of the BEC-BCS crossover through correlation measurements. In the second part, we show how a similar setup allows one to study nonlinear transport properties. In the semi-classical regime, the system is formally analogous to a Bose-Einstein condensates in optical lattices or propagation of EM fields in photonic Kerr media, allowing for simulations of similar effects with distinct advantages due to the photonic nature of the proposed system. We conclude by proposing how one of the signature effects of nonlinear dynamics, bistablity, can be experimentally observed in our set up. [Preview Abstract] |
Tuesday, March 19, 2013 2:54PM - 3:06PM |
J40.00003: Experimental investigation of a nonequilibrium delocalization-localization crossover of photons in circuit quantum electrodynamics James Raftery, Darius Sadri, Mykola Bordyuh, Devin Underwood, William Shanks, Srikanth Srinivasan, Sebastian Schmidt, Hakan Tureci, Andrew Houck We report measurements of the time-dynamics of a Jaynes-Cummings dimer. The dimer is fabricated in the circuit quantum electrodynamics (cQED) architecture, with two coupled resonators each coupled to a single transmon qubit. Such a system is predicted to exhibit three distinct behavioral regimes: delocalized, in which photons can oscillate between the two cavities; localized, in which photons are locked into a single cavity; and exiguous, in which extremely low photon numbers lead to the disappearance of locking. Dissipation in the system drives crossovers between the regimes. The experimental measurements of the on and off-site correlation functions will be presented. [Preview Abstract] |
Tuesday, March 19, 2013 3:06PM - 3:18PM |
J40.00004: On the phase transition of light in cavity QED lattices Marco Schiro, Mykola Bordyuh, Baris Oztop, Hakan Tureci Systems of strongly interacting atoms and photons, that can be realized wiring up individual cavity QED systems into lattices, are perceived as a new platform for quantum simulation. While sharing important properties with other systems of interacting quantum particles here we argue that the nature of light-matter interaction gives rise to unique features with no analogs in condensed matter or atomic physics setups. By discussing the physics of a lattice model of delocalized photons coupled locally with two-level systems through the elementary light-matter interaction described by the Rabi model, we argue that the inclusion of counter rotating terms, so far neglected, is crucial to stabilize finite-density quantum phases of correlated photons out of the vacuum, with no need for an artificially engineered chemical potential. We show that the competition between photon delocalization and Rabi non-linearity drives the system across a novel $Z_2$ parity symmetry-breaking quantum criticality between two gapped phases which shares similarities with the Dicke transition of quantum optics and the Ising critical point of quantum magnetism. We discuss the phase diagram as well as the low-energy excitation spectrum and present analytic estimates for critical quantities. [Preview Abstract] |
Tuesday, March 19, 2013 3:18PM - 3:30PM |
J40.00005: Phonon mediated quantum spin simulator made from a two-dimensional Wigner crystal in Penning traps Joseph Wang, Adam Keith, J. K. Freericks Motivated by recent advances in quantum simulations in a Penning trap, we give a theoretical description for the use of two-dimensional cold ions in a rotating trap as a quantum emulator. The collective axial phonon modes and planar modes are studied in detail, including all effects of the rotating frame. We show the character of the phonon modes and spectrum, which is crucial for engineering exotic spin interactions. In the presence of laser-ion coupling with these coherent phonon excitations, we show theoretically how the spin-spin Hamiltonian can be generated. Specifically, we notice certain parameter regimes in which the level of frustration between spins can be engineered by the coupling to the planar modes. This may be relevant to the quantum simulation of spin-glass physics or other disordered problems. [Preview Abstract] |
Tuesday, March 19, 2013 3:30PM - 3:42PM |
J40.00006: Goldstone and Higgs modes of photons inside an cavity and their detections Yu Yixiang, Yu Chen, Jinwu Ye, Wuming Liu It was well known that a broken global continuous symmetry leads to two associated collective modes: a massless Goldstone mode and a massive Anderson-Higgs amplitude mode. The two modes have been detected in various condensed matter systems and recently also in cold atom systems. The Higgs mode in particle physics was finally detected in two recent LHC experiments. In this work, we show that the two modes can also be detected in optical systems inside a cavity with only a few (artificial) atoms. We demonstrate this connection by studying the $U(1)$ Dicke (Tavis-Cummings) model where $N$ qubits (atoms) coupled to a single photon mode. We perform both $1/J=2/N$ expansion and exact diagonization (ED) study on the model. We determine the Goldstone and Higgs modes and theirs corresponding spectral weights from the system's energy spectrum and also from various photon and atom correlation functions. We find nearly perfect agreements between the results achieved from the $1/J$ calculations with those from the ED studies in all these physical quantities even when $N$ gets down even to $N = 2$. The experimental detections of both modes are also discussed. [Preview Abstract] |
Tuesday, March 19, 2013 3:42PM - 3:54PM |
J40.00007: Coherent radiation from a collection of molecules interacting with surface plasmons Michael Stopa, Semion Saikin, Alan Aspuru-Guzik A collection of molecules interacting coherently with a radiation field has dramatically different absorption and emission properties than the same collection of molecules interacting incoherently with the field. In the former case, the collective states of the molecules become important and these consist of states which radiate super-classically (Dicke superradiance) as well as states which are dark. Treated as two-level systems such a collection of molecules can be thought of as a set of spins. The product state of those spins can be transformed to a basis of states of good total ``angular momentum'' J, and good J$_{\mathrm{z}}$ (z-component of total angular momentum). Here, we construct a numerical, invertible transformation between the direct product basis and the total J basis for N total molecules. For an arbitrary product state we calculate the rate of transition via radiation out of an arbitrary state in first order perturbation theory. For an ensemble of initial states we calculate the statistical distribution of the radiance (as a function of the J$_{\mathrm{z}}$ quantum number and disorder in the couplings) of the initial state. We show that the average radiance is approximately equal to the classical value but that the distributions have an asymmetric tail toward superradiance. [Preview Abstract] |
Tuesday, March 19, 2013 3:54PM - 4:06PM |
J40.00008: Exciton-Polaritons condensates with flat bands in a two-dimensional kagome lattice Na Young Kim, Naoyuki Masumoto, Yoshihisa Yamamoto, Sven Hoefling, Alfred Forchel Microcavity exciton-polariton condensates have provided immense opportunity to investigating hydrodynamic vortex properties, superfluidity, and low energy quantum state dynamics. Recently, exciton-condensates have been trapped in various artificial periodic potential geometries: one-dimensional, two-dimensional (2D) square, triangular, and hexagonal lattices. A 2D kagome lattice has been of interest for many decades, which exhibits spin frustration, giving rise to magnetic phase order in real materials. In particular, flat bands in the 2D kagome lattice are physically interesting in that localized states in the real space are formed. Here, we realize exciton-polariton condensates in a 2D kagome lattice potential and examine their photoluminescence properties. Above quantum degeneracy threshold values, we observe meta-stable condensation in high-energy bands; the third band exhibits a signature of weaker dispersive band structures, flat band. We perform single-particle band structure calculation to compare measured band structures. [Preview Abstract] |
Tuesday, March 19, 2013 4:06PM - 4:18PM |
J40.00009: Spinor condensates of ortho- and para-positronium Yi-Hsieh Wang, Charles W. Clark In 1994, Platzman and Mills [1] considered the possibility of making a Bose-Einstein condensate (BEC) of positronium atoms (Ps). There are four low-lying states of Ps: a singlet, often called parapositronium (p-Ps); and three triplet states, often referred to as orthopositronium (o-Ps). The lifetime against electron- positron annihilation for o-Ps is a thousand times longer than that of p-Ps. By converting a long-lived triplet o-Ps BEC to a p-Ps condensate with a magnetic field, strong $\gamma$-ray emission can be generated as the outcome of the annihilation of coherent p-Ps atoms. However, inelastic scattering processes which convert p-Ps atoms to o-Ps may deplete the p-Ps population and further quench the $\gamma$ emission. We investigate this possibility by treating the system as a spinor condensate, and use the coupled time dependent Gross-Pitaevskii (GP) equations to take into account possible population-exchanging scatterings and annihilation processes in the p-Ps/o-Ps BEC mixture. This GP simulation is used to predict the $\gamma$-ray yield in realistic experimental scenarios. \\[4pt] [1] P. M. Platzman and A. P. Mills, Jr.,{\em Phys. Rev. B} {\bf 49}, 454 (1994) [Preview Abstract] |
Tuesday, March 19, 2013 4:18PM - 4:30PM |
J40.00010: Quantum simulation of non-equilibrium dynamical maps with trapped ions Philipp Schindler, Marcus M\"uller, Daniel Nigg, Thomas Monz, Julio T. Barreiro, Esteban A. Martinez, Markus Hennrich, Sebastian Diehl, Peter Zoller, Rainer Blatt Dynamical maps are central for the understanding of general state transformations of physical systems. Prime examples include classical nonlinear systems undergoing transitions to chaos, or single particle quantum mechanical counterparts showing intriguing phenomena such as dynamical localization. Here, we extend the concept of dynamical maps to an open-system, many-particle context and experimentally explore the stroboscopic dynamics of a complex many-body spin model in a universal quantum simulator using up to five ions. We generate quantum mechanical long range order by an iteration of purely dissipative maps, reveal the characteristic features of a combined coherent and dissipative non-equilibrium evolution, and develop and implement various error detection and reduction techniques that will facilitate the faithful quantum simulation of larger systems. [Preview Abstract] |
Tuesday, March 19, 2013 4:30PM - 4:42PM |
J40.00011: Quantum simulations of neutrino oscillations and the Majorana equation Changsuk Noh, Blas Rodriguez-Lara, Dimitris Angelakis Two recent works on quantum simulations of relativistic equations are presented. The first is on neutrino oscillations with trapped ions as a generalization of Dirac equation simulation in 1 spatial dimension. It is shown that with two or more ion qubits it is possible to mimic the flavour oscillations of neutrinos. The second part is on quantum simulations of the Majorana equation based on the earlier work by Casanova et al. (PRX 1, 021018). We show that by decoupling the equation, it is possible to simulate with a smaller number of qubits given that one can perform complete tomography, including the spatial degrees of freedom. [Preview Abstract] |
Tuesday, March 19, 2013 4:42PM - 4:54PM |
J40.00012: Phase Diagram of a driven-dissipative Bose-Hubbard model Alexandre Le Boit\'e, Giuliano Orso, Cristiano Ciuti In recent years, quantum fluids of light in nonlinear optical systems have attracted a lot of interest [1]. In particular, a considerable activity is presently devoted to non-equilibrium many-body phenomena with light, such as superfluid propagation and generation of topological excitations. We present here recent theoretical results on strongly correlated photons in arrays of nonlinear cavities, described by a driven-dissipative Bose-Hubbard model. We have determined the mean-field phase diagram, studied the collective excitations and quantum correlations [2], finding interesting properties which are absent in the equilibrium case.\\[4pt] [1] I. Carusotto and C. Ciuti, Rev. Mod. Phys. (in press, 2012), arXiv:1205.6500.\\[0pt] [2] A. Le Boit\'e, G. Orso, C. Ciuti, in preparation. [Preview Abstract] |
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