



01814nas a2200205   4500008004100000245007600041210006900117260001500186300001100201490000700212520120100219100001901420700002701439700001301466700002301479700002101502700002401523700002501547856003601572       2016                        eng d00aKaleidoscope of quantum phases in a long-range interacting spin-1 chain0 aKaleidoscope of quantum phases in a longrange interacting spin1   c2016/05/11  a2051150 v933 aMotivated by recent trapped-ion quantum simulation experiments, we carry out a comprehensive study of the phase diagram of a spin-1 chain with XXZ-type interactions that decay as 1/rα, using a combination of finite and infinite-size DMRG calculations, spin-wave analysis, and field theory. In the absence of long-range interactions, varying the spin-coupling anisotropy leads to four distinct phases: a ferromagnetic Ising phase, a disordered XY phase, a topological Haldane phase, and an antiferromagnetic Ising phase. If long-range interactions are antiferromagnetic and thus frustrated, we find primarily a quantitative change of the phase boundaries. On the other hand, ferromagnetic (non-frustrated) long-range interactions qualitatively impact the entire phase diagram. Importantly, for α≲3, long-range interactions destroy the Haldane phase, break the conformal symmetry of the XY phase, give rise to a new phase that spontaneously breaks a U(1) continuous symmetry, and introduce an exotic tricritical point with no direct parallel in short-range interacting spin chains. We show that the main signatures of all five phases found could be observed experimentally in the near future.
1 aGong, Zhe-Xuan1 aMaghrebi, Mohammad, F.1 aHu, Anzi1 aFoss-Feig, Michael1 aRicherme, Philip1 aMonroe, Christopher1 aGorshkov, Alexey, V.  uhttp://arxiv.org/abs/1510.0210802166nas a2200205   4500008004100000245008500041210006900126260001500195520153900210100001701749700001501766700002101781700002101802700001901823700001901842700001701861700002001878700002401898856003801922       2016                        eng d00aMany-body localization in a quantum simulator with programmable random  disorder0 aManybody localization in a quantum simulator with programmable r  c2016/06/063 a<p>When a system thermalizes it loses all local memory of its initial conditions. This is a general feature of open systems and is well described by equilibrium statistical mechanics. Even within a closed (or reversible) quantum system, where unitary time evolution retains all information about its initial state, subsystems can still thermalize using the rest of the system as an effective heat bath. Exceptions to quantum thermalization have been predicted and observed, but typically require inherent symmetries or noninteracting particles in the presence of static disorder. The prediction of many-body localization (MBL), in which disordered quantum systems can fail to thermalize in spite of strong interactions and high excitation energy, was therefore surprising and has attracted considerable theoretical attention. Here we experimentally generate MBL states by applying an Ising Hamiltonian with long-range interactions and programmably random disorder to ten spins initialized far from equilibrium. We observe the essential signatures of MBL: memory retention of the initial state, a Poissonian distribution of energy level spacings, and entanglement growth in the system at long times. Our platform can be scaled to higher numbers of spins, where detailed modeling of MBL becomes impossible due to the complexity of representing such entangled quantum states. Moreover, the high degree of control in our experiment may guide the use of MBL states as potential quantum memories in naturally disordered quantum systems.</p>1 aSmith, Jacob1 aLee, Aaron1 aRicherme, Philip1 aNeyenhuis, Brian1 aHess, Paul, W.1 aHauke, Philipp1 aHeyl, Markus1 aHuse, David, A.1 aMonroe, Christopher  uhttp://arxiv.org/abs/1508.07026v102028nas a2200229   4500008004100000245008700041210006900128260001300197300001400210490000800224520134100232100002101573700001901594700001501613700001901628700001701647700002301664700002501687700002501712700002401737856003701761       2014                        eng d00aNon-local propagation of correlations in long-range interacting quantum  systems
0 aNonlocal propagation of correlations in longrange interacting qu  c2014/7/9  a198 - 2010 v5113 a  The maximum speed with which information can propagate in a quantum many-body
system directly affects how quickly disparate parts of the system can become
correlated and how difficult the system will be to describe numerically. For
systems with only short-range interactions, Lieb and Robinson derived a
constant-velocity bound that limits correlations to within a linear effective
light cone. However, little is known about the propagation speed in systems
with long-range interactions, since the best long-range bound is too loose to
give the correct light-cone shape for any known spin model and since analytic
solutions rarely exist. In this work, we experimentally determine the spatial
and time-dependent correlations of a far-from-equilibrium quantum many-body
system evolving under a long-range Ising- or XY-model Hamiltonian. For several
different interaction ranges, we extract the shape of the light cone and
measure the velocity with which correlations propagate through the system. In
many cases we find increasing propagation velocities, which violate the
Lieb-Robinson prediction, and in one instance cannot be explained by any
existing theory. Our results demonstrate that even modestly-sized quantum
simulators are well-poised for studying complicated many-body systems that are
intractable to classical computation.
1 aRicherme, Philip1 aGong, Zhe-Xuan1 aLee, Aaron1 aSenko, Crystal1 aSmith, Jacob1 aFoss-Feig, Michael1 aMichalakis, Spyridon1 aGorshkov, Alexey, V.1 aMonroe, Christopher  uhttp://arxiv.org/abs/1401.5088v101243nas a2200181   4500008004100000245012700041210006900168260001400237490000700251520064800258100002100906700001900927700001700946700001500963700002200978700002401000856003701024       2013                        eng d00aExperimental Performance of a Quantum Simulator: Optimizing Adiabatic  Evolution and Identifying Many-Body Ground States
0 aExperimental Performance of a Quantum Simulator Optimizing Adiab  c2013/7/310 v883 a  We use local adiabatic evolution to experimentally create and determine the
ground state spin ordering of a fully-connected Ising model with up to 14
spins. Local adiabatic evolution -- in which the system evolution rate is a
function of the instantaneous energy gap -- is found to maximize the ground
state probability compared with other adiabatic methods while only requiring
knowledge of the lowest $\sim N$ of the $2^N$ Hamiltonian eigenvalues. We also
demonstrate that the ground state ordering can be experimentally identified as
the most probable of all possible spin configurations, even when the evolution
is highly non-adiabatic.
1 aRicherme, Philip1 aSenko, Crystal1 aSmith, Jacob1 aLee, Aaron1 aKorenblit, Simcha1 aMonroe, Christopher  uhttp://arxiv.org/abs/1305.2253v101289nas a2200205   4500008004100000245007500041210006900116260001300185490000800198520067800206100002100884700001900905700002200924700001700946700001500963700001900978700002500997700002401022856003701046       2013                        eng d00aQuantum Catalysis of Magnetic Phase Transitions in a Quantum Simulator0 aQuantum Catalysis of Magnetic Phase Transitions in a Quantum Sim  c2013/9/50 v1113 a  We control quantum fluctuations to create the ground state magnetic phases of
a classical Ising model with a tunable longitudinal magnetic field using a
system of 6 to 10 atomic ion spins. Due to the long-range Ising interactions,
the various ground state spin configurations are separated by multiple
first-order phase transitions, which in our zero temperature system cannot be
driven by thermal fluctuations. We instead use a transverse magnetic field as a
quantum catalyst to observe the first steps of the complete fractal devil's
staircase, which emerges in the thermodynamic limit and can be mapped to a
large number of many-body and energy-optimization problems.
1 aRicherme, Philip1 aSenko, Crystal1 aKorenblit, Simcha1 aSmith, Jacob1 aLee, Aaron1 aIslam, Rajibul1 aCampbell, Wesley, C.1 aMonroe, Christopher  uhttp://arxiv.org/abs/1303.6983v2