02312nas a2200217 4500008004100000245006500041210006400106260001400170490000700184520168700191100001901878700001901897700002001916700002001936700002301956700001601979700001901995700002502014700001802039856003702057 2020 eng d00aHierarchy of linear light cones with long-range interactions0 aHierarchy of linear light cones with longrange interactions c5/29/20200 v103 a
In quantum many-body systems with local interactions, quantum information and entanglement cannot spread outside of a "linear light cone," which expands at an emergent velocity analogous to the speed of light. Yet most non-relativistic physical systems realized in nature have long-range interactions: two degrees of freedom separated by a distance r interact with potential energy V(r)∝1/rα. In systems with long-range interactions, we rigorously establish a hierarchy of linear light cones: at the same α, some quantum information processing tasks are constrained by a linear light cone while others are not. In one spatial dimension, commutators of local operators 〈ψ|[Ox(t),Oy]|ψ〉 are negligible in every state |ψ〉 when |x−y|≳vt, where v is finite when α>3 (Lieb-Robinson light cone); in a typical state |ψ〉 drawn from the infinite temperature ensemble, v is finite when α>52 (Frobenius light cone); in non-interacting systems, v is finite in every state when α>2 (free light cone). These bounds apply to time-dependent systems and are optimal up to subalgebraic improvements. Our theorems regarding the Lieb-Robinson and free light cones, and their tightness, also generalize to arbitrary dimensions. We discuss the implications of our bounds on the growth of connected correlators and of topological order, the clustering of correlations in gapped systems, and the digital simulation of systems with long-range interactions. In addition, we show that quantum state transfer and many-body quantum chaos are bounded by the Frobenius light cone, and therefore are poorly constrained by all Lieb-Robinson bounds.
1 aTran, Minh, C.1 aChen, Chi-Fang1 aEhrenberg, Adam1 aGuo, Andrew, Y.1 aDeshpande, Abhinav1 aHong, Yifan1 aGong, Zhe-Xuan1 aGorshkov, Alexey, V.1 aLucas, Andrew uhttps://arxiv.org/abs/2001.1150901772nas a2200169 4500008004100000245006700041210006600108260001300174490000800187520126400195100002001459700001901479700002301498700002501521700001901546856003701565 2020 eng d00aSignaling and Scrambling with Strongly Long-Range Interactions0 aSignaling and Scrambling with Strongly LongRange Interactions c7/8/20200 v1023 aStrongly long-range interacting quantum systems---those with interactions decaying as a power-law 1/rα in the distance r on a D-dimensional lattice for α≤D---have received significant interest in recent years. They are present in leading experimental platforms for quantum computation and simulation, as well as in theoretical models of quantum information scrambling and fast entanglement creation. Since no notion of locality is expected in such systems, a general understanding of their dynamics is lacking. As a first step towards rectifying this problem, we prove two new Lieb-Robinson-type bounds that constrain the time for signaling and scrambling in strongly long-range interacting systems, for which no tight bounds were previously known. Our first bound applies to systems mappable to free-particle Hamiltonians with long-range hopping, and is saturable for α≤D/2. Our second bound pertains to generic long-range interacting spin Hamiltonians, and leads to a tight lower bound for the signaling time to extensive subsets of the system for all α<D. This result also lower-bounds the scrambling time, and suggests a path towards achieving a tight scrambling bound that can prove the long-standing fast scrambling conjecture.
1 aGuo, Andrew, Y.1 aTran, Minh, C.1 aChilds, Andrew, M.1 aGorshkov, Alexey, V.1 aGong, Zhe-Xuan uhttps://arxiv.org/abs/1906.0266201814nas a2200169 4500008004100000245006700041210006600108260001400174490000800188520130400196100001701500700002201517700002401539700002501563700001901588856003701607 2019 eng d00aProbing ground-state phase transitions through quench dynamics0 aProbing groundstate phase transitions through quench dynamics c9/11/20190 v1233 aThe study of quantum phase transitions requires the preparation of a many-body system near its ground state, a challenging task for many experimental systems. The measurement of quench dynamics, on the other hand, is now a routine practice in most cold atom platforms. Here we show that quintessential ingredients of quantum phase transitions can be probed directly with quench dynamics in integrable and nearly integrable systems. As a paradigmatic example, we study global quench dynamics in a transverse-field Ising model with either short-range or long-range interactions. When the model is integrable, we discover a new dynamical critical point with a non-analytic signature in the short-range correlators. The location of the dynamical critical point matches that of the quantum critical point and can be identified using a finite-time scaling method. We extend this scaling picture to systems near integrability and demonstrate the continued existence of a dynamical critical point detectable at prethermal time scales. Therefore, our method can be used to approximately locate the quantum critical point. The scaling method is also relevant to experiments with finite time and system size, and our predictions are testable in near-term experiments with trapped ions and Rydberg atoms.
1 aTitum, Paraj1 aIosue, Joseph, T.1 aGarrison, James, R.1 aGorshkov, Alexey, V.1 aGong, Zhe-Xuan uhttps://arxiv.org/abs/1809.0637701449nas a2200169 4500008004100000245008800041210006900129260001500198490000800213520091700221100001601138700002401154700002001178700001901198700002501217856003701242 2018 eng d00aAsymmetric Particle Transport and Light-Cone Dynamics Induced by Anyonic Statistics0 aAsymmetric Particle Transport and LightCone Dynamics Induced by c2018/12/200 v1213 aWe study the non-equilibrium dynamics of Abelian anyons in a one-dimensional system. We find that the interplay of anyonic statistics and interactions gives rise to spatially asymmetric particle transport together with a novel dynamical symmetry that depends on the anyonic statistical angle and the sign of interactions. Moreover, we show that anyonic statistics induces asymmetric spreading of quantum information, characterized by asymmetric light cones of out-of-time-ordered correlators. Such asymmetric dynamics is in sharp contrast with the dynamics of conventional fermions or bosons, where both the transport and information dynamics are spatially symmetric. We further discuss experiments with cold atoms where the predicted phenomena can be observed using state-of-the-art technologies. Our results pave the way toward experimentally probing anyonic statistics through non-equilibrium dynamics.
1 aLiu, Fangli1 aGarrison, James, R.1 aDeng, Dong-Ling1 aGong, Zhe-Xuan1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1809.0261401217nas a2200169 4500008004100000245006400041210006200105260001500167300001100182490000800193520070900201100001900910700002300929700003300952700002500985856003701010 2017 eng d00a{E}ntanglement area laws for long-range interacting systems0 aE ntanglement area laws for longrange interacting systems c2017/07/31 a0505010 v1193 aWe prove that the entanglement entropy of any state evolved under an arbitrary 1/rα long-range-interacting D-dimensional lattice spin Hamiltonian cannot change faster than a rate proportional to the boundary area for any α > D + 1. We also prove that for any α > 2D + 2, the ground state of such a Hamiltonian satisfies the entanglement area law if it can be transformed along a gapped adiabatic path into a ground state known to satisfy the area law. These results significantly generalize their existing counterparts for short-range interacting systems, and are useful for identifying dynamical phase transitions and quantum phase transitions in the presence of long-range interactions.
1 aGong, Zhe-Xuan1 aFoss-Feig, Michael1 aBrandão, Fernando, G. S. L.1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1702.0536827528nas a2200181 45000080041000002450087000412100069001282600015001973000011002124900008002235202696300231100002227194700001927216700002627235700002327261700002527284856003727309 2017 eng d00aFast State Transfer and Entanglement Renormalization Using Long-Range Interactions0 aFast State Transfer and Entanglement Renormalization Using LongR c2017/10/25 a1705030 v1193 aIn short-range interacting systems, the speed at which entanglement can be established between two separated points is limited by a constant Lieb-Robinson velocity. Long-range interacting systems are capable of faster entanglement generation, but the degree of the speed-up possible is an open question. In this paper, we present a protocol capable of transferring a quantum state across a distance L in d dimensions using long-range interactions with strength bounded by 1/rα. If α<d, the state transfer time is asymptotically independent of L; if α=d, the time is logarithmic in distance L; if d<α<d+1, transfer occurs in time proportional to Lα−d; and if α≥d+1, it occurs in time proportional to L. We then use this protocol to upper bound the time required to create a state specified by a MERA (multiscale entanglement renormalization ansatz) tensor network, and show that, if the linear size of the MERA state is L, then it can be created in time that scales with L identically to state transfer up to multiplicative logarithmic corrections.
1 aEldredge, Zachary1 aGong, Zhe-Xuan1 aMoosavian, Ali, Hamed1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1612.0244201058nas a2200133 4500008004100000245007000041210006800111520062100179100001900800700002400819700001900843700002500862856003700887 2017 eng d00aLieb-Robinson bounds on n-partite connected correlation functions0 aLiebRobinson bounds on npartite connected correlation functions3 aLieb and Robinson provided bounds on how fast bipartite connected correlations can arise in systems with only short-range interactions. We generalize Lieb-Robinson bounds on bipartite connected correlators to multipartite connected correlators. The bounds imply that an n-partite connected correlator can reach unit value in constant time. Remarkably, the bounds also allow for an n-partite connected correlator to reach a value that is exponentially large with system size in constant time, a feature which stands in contrast to bipartite connected correlations. We provide explicit examples of such systems.
1 aTran, Minh, C.1 aGarrison, James, R.1 aGong, Zhe-Xuan1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1705.0435504237nas a2200157 4500008004100000245006100041210005900102260001500161490000700176520377200183100001903955700002403974700001903998700002504017856003704042 2017 eng d00aLieb-Robinson bounds on n-partite connected correlations0 aLiebRobinson bounds on npartite connected correlations c2017/11/270 v963 aLieb and Robinson provided bounds on how fast bipartite connected correlations can arise in systems with only short-range interactions. We generalize Lieb-Robinson bounds on bipartite connected correlators to multipartite connected correlators. The bounds imply that an n-partite connected correlator can reach unit value in constant time. Remarkably, the bounds also allow for an n-partite connected correlator to reach a value that is exponentially large with system size in constant time, a feature which stands in contrast to bipartite connected correlations. We provide explicit examples of such systems.
1 aTran, Minh, C.1 aGarrison, James, R.1 aGong, Zhe-Xuan1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1705.0435500514nas a2200157 4500008004100000245006700041210006600108260001500174300001100189490000700200100002700207700001900234700002300253700002500276856005500301 2016 eng d00aCausality and quantum criticality in long-range lattice models0 aCausality and quantum criticality in longrange lattice models c2016/03/17 a1251280 v931 aMaghrebi, Mohammad, F.1 aGong, Zhe-Xuan1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttp://link.aps.org/doi/10.1103/PhysRevB.93.12512801582nas a2200169 4500008004100000245006700041210006600108260001500174300001100189490000700200520107500207100002701282700001901309700002301328700002501351856003601376 2016 eng d00aCausality and quantum criticality with long-range interactions0 aCausality and quantum criticality with longrange interactions c2016/03/17 a1251280 v923 a Quantum lattice systems with long-range interactions often exhibit
drastically different behavior than their short-range counterparts. In
particular, because they do not satisfy the conditions for the Lieb-Robinson
theorem, they need not have an emergent relativistic structure in the form of a
light cone. Adopting a field-theoretic approach, we study the one-dimensional
transverse-field Ising model and a fermionic model with long-range
interactions, explore their critical and near-critical behavior, and
characterize their response to local perturbations. We deduce the dynamic
critical exponent, up to the two-loop order within the renormalization group
theory, which we then use to characterize the emergent causal behavior. We show
that beyond a critical value of the power-law exponent of long-range
interactions, the dynamics effectively becomes relativistic. Various other
critical exponents describing correlations in the ground state, as well as
deviations from a linear causal cone, are deduced for a wide range of the
power-law exponent.
1 aMaghrebi, Mohammad, F.1 aGong, Zhe-Xuan1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1508.0090601507nas a2200145 4500008004100000245007200041210006900113260001500182520103700197100002301234700001901257700002501276700002301301856003701324 2016 eng d00aEntanglement and spin-squeezing without infinite-range interactions0 aEntanglement and spinsqueezing without infiniterange interaction c2016/12/223 aInfinite-range interactions are known to facilitate the production of highly entangled states with applications in quantum information and metrology. However, many experimental systems have interactions that decay with distance, and the achievable benefits in this context are much less clear. Combining recent exact solutions with a controlled expansion in the system size, we analyze quench dynamics in Ising models with power-law (1/r α ) interactions in D dimensions, thereby expanding the understanding of spin squeezing into a broad and experimentally relevant context. In spatially homogeneous systems, we show that for small α the scaling of squeezing with system size is identical to the infinite-range (α = 0) case. This indifference to the interaction range persists up to a critical value α = 2D/3, above which squeezing degrades continuously. Boundaryinduced inhomogeneities present in most experimental systems modify this picture, but it nevertheless remains qualitatively correct for finite-sized systems.
1 aFoss-Feig, Michael1 aGong, Zhe-Xuan1 aGorshkov, Alexey, V.1 aClark, Charles, W. uhttps://arxiv.org/abs/1612.0780501814nas 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/1510.0210809346nas a2200181 4500008004100000245005500041210005400096260001500150520881500165100001908980700001608999700002309015700002409038700002009062700002009082700002509102856003709127 2016 eng d00aSteady-state superradiance with Rydberg polaritons0 aSteadystate superradiance with Rydberg polaritons c2016/11/023 aA steady-state superradiant laser can be used to generate ultranarrow-linewidth light, and thus has important applications in the fields of quantum information and precision metrology. However, the light produced by such a laser is still essentially classical. Here, we show that the introduction of a Rydberg medium into a cavity containing atoms with a narrow optical transition can lead to the steady-state superradiant emission of ultranarrow-linewidth nonclassical light. The cavity nonlinearity induced by the Rydberg medium strongly modifies the superradiance threshold, and leads to a Mollow triplet in the cavity output spectrum−this behavior can be understood as an unusual analogue of resonance fluorescence. The cavity output spectrum has an extremely sharp central peak, with a linewidth that can be far narrower than that of a classical superradiant laser. This unprecedented spectral sharpness, together with the nonclassical nature of the light, could lead to new applications in which spectrally pure quantum light is desired.
1 aGong, Zhe-Xuan1 aXu, Minghui1 aFoss-Feig, Michael1 aThompson, James, K.1 aRey, Ana, Maria1 aHolland, Murray1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1611.0079701535nas a2200193 4500008004100000245005200041210005100093260001500144300001100159490000700170520099900177100001901176700002701195700001301222700002201235700002301257700002501280856003601305 2016 eng d00aTopological phases with long-range interactions0 aTopological phases with longrange interactions c2016/01/08 a0411020 v933 a Topological phases of matter are primarily studied in quantum many-body
systems with short-range interactions. Whether various topological phases can
survive in the presence of long-range interactions, however, is largely
unknown. Here we show that a paradigmatic example of a symmetry-protected
topological phase, the Haldane phase of an antiferromagnetic spin-1 chain,
surprisingly remains intact in the presence of arbitrarily slowly decaying
power-law interactions. The influence of long-range interactions on the
topological order is largely quantitative, and we expect similar results for
more general systems. Our conclusions are based on large-scale
matrix-product-state simulations and two complementary effective-field-theory
calculations. The striking agreement between the numerical and analytical
results rules out finite-size effects. The topological phase considered here
should be experimentally observable in a recently developed trapped-ion quantum
simulator.
1 aGong, Zhe-Xuan1 aMaghrebi, Mohammad, F.1 aHu, Anzi1 aWall, Michael, L.1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1505.0314601576nas a2200133 4500008004100000245010700041210006900148260001500217520110300232100002701335700001901362700002501381856003601406 2015 eng d00aContinuous symmetry breaking and a new universality class in 1D long-range interacting quantum systems0 aContinuous symmetry breaking and a new universality class in 1D c2015/10/053 aContinuous symmetry breaking (CSB) in low-dimensional systems, forbidden by the Mermin-Wagner theorem for short-range interactions, may take place in the presence of slowly decaying long-range interactions. Nevertheless, there is no stringent bound on how slowly interactions should decay to give rise to CSB in 1D quantum systems at zero temperature. Here, we study a long-range interacting spin chain with U(1) symmetry and power-law interactions V(r)∼1/rα, directly relevant to ion-trap experiments. Using bosonization and renormalization group theory, we find CSB for α smaller than a critical exponent αc(≤3) depending on the microscopic parameters of the model. Furthermore, the transition from the gapless XY phase to the gapless CSB phase is mediated by the breaking of conformal symmetry due to long-range interactions, and is described by a new universality class akin to the Berezinskii-Kosterlitz-Thouless transition. Our analytical findings are in good agreement with a numerical calculation. Signatures of the CSB phase should be accessible in existing trapped-ion experiments.1 aMaghrebi, Mohammad, F.1 aGong, Zhe-Xuan1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1510.0132501522nas a2200169 4500008004100000245007200041210006900113260001500182300001100197490000800208520100900216100002301225700001901248700002301267700002501290856003701315 2015 eng d00aNearly-linear light cones in long-range interacting quantum systems0 aNearlylinear light cones in longrange interacting quantum system c2015/04/13 a1572010 v1143 a In non-relativistic quantum theories with short-range Hamiltonians, a
velocity $v$ can be chosen such that the influence of any local perturbation is
approximately confined to within a distance $r$ until a time $t \sim r/v$,
thereby defining a linear light cone and giving rise to an emergent notion of
locality. In systems with power-law ($1/r^{\alpha}$) interactions, when
$\alpha$ exceeds the dimension $D$, an analogous bound confines influences to
within a distance $r$ only until a time $t\sim(\alpha/v)\log r$, suggesting
that the velocity, as calculated from the slope of the light cone, may grow
exponentially in time. We rule out this possibility; light cones of power-law
interacting systems are algebraic for $\alpha>2D$, becoming linear as
$\alpha\rightarrow\infty$. Our results impose strong new constraints on the
growth of correlations and the production of entangled states in a variety of
rapidly emerging, long-range interacting atomic, molecular, and optical
systems.
1 aFoss-Feig, Michael1 aGong, Zhe-Xuan1 aClark, Charles, W.1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1410.3466v102028nas 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/1401.5088v101399nas a2200157 4500008004100000245006700041210006600108260001400174490000800188520091600196100001901112700002301131700002501154700002501179856003701204 2014 eng d00aPersistence of locality in systems with power-law interactions0 aPersistence of locality in systems with powerlaw interactions c2014/7/160 v1133 a Motivated by recent experiments with ultra-cold matter, we derive a new bound
on the propagation of information in $D$-dimensional lattice models exhibiting
$1/r^{\alpha}$ interactions with $\alpha>D$. The bound contains two terms: One
accounts for the short-ranged part of the interactions, giving rise to a
bounded velocity and reflecting the persistence of locality out to intermediate
distances, while the other contributes a power-law decay at longer distances.
We demonstrate that these two contributions not only bound but, except at long
times, \emph{qualitatively reproduce} the short- and long-distance dynamical
behavior following a local quench in an $XY$ chain and a transverse-field Ising
chain. In addition to describing dynamics in numerous intractable long-range
interacting lattice models, our results can be experimentally verified in a
variety of ultracold-atomic and solid-state systems.
1 aGong, Zhe-Xuan1 aFoss-Feig, Michael1 aMichalakis, Spyridon1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1401.6174v201205nas a2200145 4500008004100000245007600041210006900117260001500186490000700201520076300208100001500971700001900986700001701005856003701022 2013 eng d00aIndividual Addressing in Quantum Computation through Spatial Refocusing0 aIndividual Addressing in Quantum Computation through Spatial Ref c2013/11/210 v883 a Separate addressing of individual qubits is a challenging requirement for
scalable quantum computation, and crosstalk between operations on neighboring
qubits remains as a significant source of noise for current experimental
implementation of multi-qubit platforms. We propose a scheme based on spatial
refocusing from interference of several coherent laser beams to significantly
reduce the crosstalk noise for any type of quantum gates. A general framework
is developed for the spatial refocusing technique, in particular with practical
Gaussian beams, and we show under typical experimental conditions, the
crosstalk-induced infidelity of quantum gates can be reduced by several orders
of magnitude with a moderate cost of a few correction laser beams.
1 aShen, Chao1 aGong, Zhe-Xuan1 aDuan, Luming uhttp://arxiv.org/abs/1305.2798v301207nas a2200145 4500008004100000245008800041210006900129260001500198300001100213490000700224520075600231100001900987700001801006856003701024 2013 eng d00aPrethermalization and dynamical transition in an isolated trapped ion spin chain
0 aPrethermalization and dynamical transition in an isolated trappe c2013/11/26 a1130510 v153 a We propose an experimental scheme to observe prethermalization and dynamical
transition in one-dimensional XY spin chain with long range interaction and
inhomogeneous lattice spacing, which can be readily implemented with the
recently developed trapped-ion quantum simulator. Local physical observables
are found to relax to prethermal values at intermediate time scale, followed by
complete relaxation to thermal values at much longer time. The physical origin
of prethermalization is explained by spotting a non-trivial structure in lower
half of the energy spectrum. The dynamical behavior of the system is shown to
cross difference phases when the interaction range is continuously tuned,
indicating the existence of dynamical phase transition.
1 aGong, Zhe-Xuan1 aDuan, L., -M. uhttp://arxiv.org/abs/1305.0985v101995nas a2200205 4500008004100000245005100041210005100092260001300143490000700156520142000163100002001583700001901603700002301622700002401645700001801669700002301687700001701710700002501727856003701752 2013 eng d00aQuantum Logic between Remote Quantum Registers0 aQuantum Logic between Remote Quantum Registers c2013/2/60 v873 a We analyze two approaches to quantum state transfer in solid-state spin
systems. First, we consider unpolarized spin-chains and extend previous
analysis to various experimentally relevant imperfections, including quenched
disorder, dynamical decoherence, and uncompensated long range coupling. In
finite-length chains, the interplay between disorder-induced localization and
decoherence yields a natural optimal channel fidelity, which we calculate.
Long-range dipolar couplings induce a finite intrinsic lifetime for the
mediating eigenmode; extensive numerical simulations of dipolar chains of
lengths up to L=12 show remarkably high fidelity despite these decay processes.
We further consider the extension of the protocol to bosonic systems of coupled
oscillators. Second, we introduce a quantum mirror based architecture for
universal quantum computing which exploits all of the spins in the system as
potential qubits. While this dramatically increases the number of qubits
available, the composite operations required to manipulate "dark" spin qubits
significantly raise the error threshold for robust operation. Finally, as an
example, we demonstrate that eigenmode-mediated state transfer can enable
robust long-range logic between spatially separated Nitrogen-Vacancy registers
in diamond; numerical simulations confirm that high fidelity gates are
achievable even in the presence of moderate disorder.
1 aYao, Norman, Y.1 aGong, Zhe-Xuan1 aLaumann, Chris, R.1 aBennett, Steven, D.1 aDuan, L., -M.1 aLukin, Mikhail, D.1 aJiang, Liang1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1206.0014v101592nas a2200205 4500008004100000245012500041210006900166260001500235520091800250100001801168700002001186700002601206700002001232700001901252700001901271700001801290700002101308700002001329856003701349 2012 eng d00aPhotonic quantum simulation of ground state configurations of Heisenberg square and checkerboard lattice spin systems
0 aPhotonic quantum simulation of ground state configurations of He c2012/05/123 a Photonic quantum simulators are promising candidates for providing insight
into other small- to medium-sized quantum systems. The available photonic
quantum technology is reaching the state where significant advantages arise for
the quantum simulation of interesting questions in Heisenberg spin systems.
Here we experimentally simulate such spin systems with single photons and
linear optics. The effective Heisenberg-type interactions among individual
single photons are realized by quantum interference at the tunable direction
coupler followed by the measurement process. The effective interactions are
characterized by comparing the entanglement dynamics using pairwise concurrence
of a four-photon quantum system. We further show that photonic quantum
simulations of generalized Heisenberg interactions on a four-site square
lattice and a six-site checkerboard lattice are in reach of current technology.
1 aMa, Xiao-song1 aDakic, Borivoje1 aKropatsche, Sebastian1 aNaylor, William1 aChan, Yang-hao1 aGong, Zhe-Xuan1 aDuan, Lu-ming1 aZeilinger, Anton1 aWalther, Philip uhttp://arxiv.org/abs/1205.2801v101417nas a2200253 4500008004100000245008300041210006900124260001500193300001100208490000700219520068500226100002200911700001600933700002300949700001900972700002300991700001901014700001801033700001701051700001801068700001601086700002401102856003701126 2012 eng d00aQuantum Simulation of Spin Models on an Arbitrary Lattice with Trapped Ions
0 aQuantum Simulation of Spin Models on an Arbitrary Lattice with T c2012/09/27 a0950240 v143 a A collection of trapped atomic ions represents one of the most attractive
platforms for the quantum simulation of interacting spin networks and quantum
magnetism. Spin-dependent optical dipole forces applied to an ion crystal
create long-range effective spin-spin interactions and allow the simulation of
spin Hamiltonians that possess nontrivial phases and dynamics. Here we show how
appropriate design of laser fields can provide for arbitrary multidimensional
spin-spin interaction graphs even for the case of a linear spatial array of
ions. This scheme uses currently existing trap technology and is scalable to
levels where classical methods of simulation are intractable.
1 aKorenblit, Simcha1 aKafri, Dvir1 aCampbell, Wess, C.1 aIslam, Rajibul1 aEdwards, Emily, E.1 aGong, Zhe-Xuan1 aLin, Guin-Dar1 aDuan, Luming1 aKim, Jungsang1 aKim, Kihwan1 aMonroe, Christopher uhttp://arxiv.org/abs/1201.0776v100674nas a2200193 4500008004100000245006100041210005900102260001500161520012900176100001700305700001900322700001800341700001700359700001600376700001600392700001800408700001700426856003700443 2012 eng d00aReply to Comment on "Space-Time Crystals of Trapped Ions0 aReply to Comment on SpaceTime Crystals of Trapped Ions c2012/10/153 a This is a reply to the comment from Patrick Bruno (arXiv:1211.4792) on our
paper (Phys. Rev. Lett. 109, 163001 (2012)).
1 aLi, Tongcang1 aGong, Zhe-Xuan1 aYin, Zhang-qi1 aQuan, H., T.1 aYin, Xiaobo1 aZhang, Peng1 aDuan, L., -M.1 aZhang, Xiang uhttp://arxiv.org/abs/1212.6959v201472nas a2200217 4500008004100000245004000041210003900081260001500120300001100135490000800146520090500154100001701059700001901076700001801095700001701113700001601130700001601146700001601162700001701178856005901195 2012 eng d00aSpace-Time Crystals of Trapped Ions0 aSpaceTime Crystals of Trapped Ions c2012/10/19 a1630010 v1093 aSpontaneous symmetry breaking can lead to the formation of time crystals, as well as spatial crystals. Here we propose a space-time crystal of trapped ions and a method to realize it experimentally by confining ions in a ring-shaped trapping potential with a static magnetic field. The ions spontaneously form a spatial ring crystal due to Coulomb repulsion. This ion crystal can rotate persistently at the lowest quantum energy state in magnetic fields with fractional fluxes. The persistent rotation of trapped ions produces the temporal order, leading to the formation of a space-time crystal. We show that these space-time crystals are robust for direct experimental observation. We also study the effects of finite temperatures on the persistent rotation. The proposed space-time crystals of trapped ions provide a new dimension for exploring many-body physics and emerging properties of matter.1 aLi, Tongcang1 aGong, Zhe-Xuan1 aYin, Zhang-Qi1 aQuan, H., T.1 aYin, Xiaobo1 aZhang, Peng1 aDuan, L.-M.1 aZhang, Xiang uhttp://link.aps.org/doi/10.1103/PhysRevLett.109.16300100744nas a2200121 4500008004100000245009800041210006900139260001500208520032500223100001900548700001800567856003700585 2011 eng d00aComment on "Foundation of Statistical Mechanics under Experimentally Realistic Conditions"
0 aComment on Foundation of Statistical Mechanics under Experimenta c2011/09/223 a Reimann [Phys. Rev. Lett. 101, 190403 (2008)] claimed that generic isolated
macroscopic quantum system will equilibrate under experimentally realistic
conditions by proving a theorem. We here show that the proof is invalid for
most many-body systems and is unable to demonstrate equilibration in realistic
experiment.
1 aGong, Zhe-Xuan1 aDuan, L., -M. uhttp://arxiv.org/abs/1109.4696v101276nas a2200157 4500008004100000245008200041210006900123260001500192300001100207490000700218520080100225100001901026700001801045700001801063856003701081 2011 eng d00aDynamics of Overhauser Field under nuclear spin diffusion in a quantum dot
0 aDynamics of Overhauser Field under nuclear spin diffusion in a q c2011/03/25 a0330360 v133 a The coherence of electron spin can be significantly enhanced by locking the
Overhauser field from nuclear spins using the nuclear spin preparation. We
propose a theoretical model to calculate the long time dynamics of the
Overhauser field under intrinsic nuclear spin diffusion in a quantum dot. We
obtain a simplified diffusion equation that can be numerically solved and show
quantitatively how the Knight shift and the electron-mediated nuclear spin
flip-flop affect the nuclear spin diffusion. The results explain several recent
experimental observations, where the decay time of Overhauser field is measured
under different configurations, including variation of the external magnetic
field, the electron spin configuration in a double dot, and the initial nuclear
spin polarization rate.
1 aGong, Zhe-Xuan1 aYin, Zhang-qi1 aDuan, L., -M. uhttp://arxiv.org/abs/0912.4322v101404nas a2200193 4500008004100000245006800041210006800109260001400177490000800191520083700199100002001036700001701056700002501073700001901098700001501117700001801132700002301150856003701173 2011 eng d00aRobust Quantum State Transfer in Random Unpolarized Spin Chains0 aRobust Quantum State Transfer in Random Unpolarized Spin Chains c2011/1/270 v1063 a We propose and analyze a new approach for quantum state transfer between
remote spin qubits. Specifically, we demonstrate that coherent quantum coupling
between remote qubits can be achieved via certain classes of random,
unpolarized (infinite temperature) spin chains. Our method is robust to
coupling strength disorder and does not require manipulation or control over
individual spins. In principle, it can be used to attain perfect state transfer
over arbitrarily long range via purely Hamiltonian evolution and may be
particularly applicable in a solid-state quantum information processor. As an
example, we demonstrate that it can be used to attain strong coherent coupling
between Nitrogen-Vacancy centers separated by micrometer distances at room
temperature. Realistic imperfections and decoherence effects are analyzed.
1 aYao, Norman, Y.1 aJiang, Liang1 aGorshkov, Alexey, V.1 aGong, Zhe-Xuan1 aZhai, Alex1 aDuan, L., -M.1 aLukin, Mikhail, D. uhttp://arxiv.org/abs/1011.2762v201144nas a2200145 4500008004100000245010200041210006900143260001500212490000800227520067200235100001900907700001700926700001800943856003700961 2010 eng d00aTemperature driven structural phase transition for trapped ions and its experimental detection
0 aTemperature driven structural phase transition for trapped ions c2010/12/290 v1053 a A Wigner crystal formed with trapped ion can undergo structural phase
transition, which is determined only by the mechanical conditions on a
classical level. Instead of this classical result, we show that through
consideration of quantum and thermal fluctuation, a structural phase transition
can be solely driven by change of the system's temperature. We determine a
finite-temperature phase diagram for trapped ions using the renormalization
group method and the path integral formalism, and propose an experimental
scheme to observe the predicted temperature-driven structural phase transition,
which is well within the reach of the current ion trap technology.
1 aGong, Zhe-Xuan1 aLin, G., -D.1 aDuan, L., -M. uhttp://arxiv.org/abs/1009.0089v101191nas a2200145 4500008004100000245007100041210006900112260001400181300001600195490000700211520075200218100001900970700001900989856003701008 2008 eng d00aEfficient scheme for one-way quantum computing in thermal cavities0 aEfficient scheme for oneway quantum computing in thermal cavitie c2008/4/12 a2997 - 30040 v473 a We propose a practical scheme for one-way quantum computing based on
efficient generation of 2D cluster state in thermal cavities. We achieve a
controlled-phase gate that is neither sensitive to cavity decay nor to thermal
field by adding a strong classical field to the two-level atoms. We show that a
2D cluster state can be generated directly by making every two atoms collide in
an array of cavities, with numerically calculated parameters and appropriate
operation sequence that can be easily achieved in practical Cavity QED
experiments. Based on a generated cluster state in Box$^{(4)}$ configuration,
we then implement Grover's search algorithm for four database elements in a
very simple way as an example of one-way quantum computing.
1 aYang, Wen-Xing1 aGong, Zhe-Xuan uhttp://arxiv.org/abs/0704.2297v101229nas a2200145 4500008004100000245011300041210006900154260001500223300001600238490000700254520074000261100001901001700001901020856004401039 2007 eng d00aPractical scheme for quantum dense coding between three parties using microwave radiation in trapped ions
0 aPractical scheme for quantum dense coding between three parties c2007/03/28 a1245 - 12520 v403 a We propose a practical scheme for implementing two-dimension quantum dense
coding (QDC) between three parties through manipulating three ions confined in
microtraps addressed by microwaves and assisted by a magnetic field gradient.
The ions in our scheme are not required to be strictly cooled to the
vibrational ground state because single-qubit and multi-qubit operations are
made via Ising terms, in which the vibrational modes of the ions remain
unchanged throughout the scheme, rendering our scheme robust to the heating of
the ions. We also present the detailed steps and parameters for implementing
the three-party QDC experimentally and show that the proposed scheme is within
the current techniques of ion-trap experiments.
1 aYang, Wen-Xing1 aGong, Zhe-Xuan uhttp://arxiv.org/abs/quant-ph/0702062v101118nas a2200145 4500008004100000245008400041210006900125260001500194300001400209490000700223520066000230100001900890700001900909856004400928 2007 eng d00aSimple scheme for implementing the Deutsch-Jozsa algorithm in thermal cavity
0 aSimple scheme for implementing the DeutschJozsa algorithm in the c2007/01/05 a155 - 1610 v403 a We present a simple scheme to implement the Deutsch-Jozsa algorithm based on
two-atom interaction in a thermal cavity. The photon-number-dependent parts in
the evolution operator are canceled with the strong resonant classical field
added. As a result, our scheme is immune to thermal field, and does not require
the cavity to remain in the vacuum state throughout the procedure. Besides,
large detuning between the atoms and the cavity is not necessary neither,
leading to potential speed up of quantum operation. Finally, we show by
numerical simulation that the proposed scheme is equal to demonstrate the
Deutsch-Jozsa algorithm with high fidelity.
1 aYang, Wen-Xing1 aGong, Zhe-Xuan uhttp://arxiv.org/abs/quant-ph/0611225v201021nas a2200109 4500008004100000245007100041210006900112260001500181520065200196100001900848856004400867 2006 eng d00aEffective error-suppression scheme for reversible quantum computer0 aEffective errorsuppression scheme for reversible quantum compute c2006/08/203 a We construct a new error-suppression scheme that makes use of the adjoint of
reversible quantum algorithms. For decoherence induced errors such as
depolarization, it is presented that provided the depolarization error
probability is less than 1, our scheme can exponentially reduce the final
output error rate to zero using a number of cycles, and the output state can be
coherently sent to another stage of quantum computation process. Besides,
experimental set-ups via optical approach have been proposed using Grover's
search algorithm as an example. Some further discussion on the benefits and
limitations of the scheme is given in the end.
1 aGong, Zhe-Xuan uhttp://arxiv.org/abs/quant-ph/0608152v4