01932nas a2200181 4500008004100000245005700041210005700098260001300155520138000168100002501548700002001573700002201593700002701615700002301642700002501665700002301690856003701713 2020 eng d00aCritical Theory for the Breakdown of Photon Blockade0 aCritical Theory for the Breakdown of Photon Blockade c6/9/20203 a
Photon blockade is the result of the interplay between the quantized nature of light and strong optical nonlinearities, whereby strong photon-photon repulsion prevents a quantum optical system from absorbing multiple photons. We theoretically study a single atom coupled to the light field, described by the resonantly driven Jaynes--Cummings model, in which case the photon blockade breaks down in a second order phase transition at a critical drive strength. We show that this transition is associated to the spontaneous breaking of an anti-unitary PT-symmetry. Within a semiclassical approximation we calculate the expectation values of observables in the steady state. We then move beyond the semiclassical approximation and approach the critical point from the disordered (blockaded) phase by reducing the Lindblad quantum master equation to a classical rate equation that we solve. The width of the steady-state distribution in Fock space is found to diverge as we approach the critical point with a simple power-law, allowing us to calculate the critical scaling of steady state observables without invoking mean-field theory. We propose a simple physical toy model for biased diffusion in the space of occupation numbers, which captures the universal properties of the steady state. We list several experimental platforms where this phenomenon may be observed.
1 aCurtis, Jonathan, B.1 aBoettcher, Igor1 aYoung, Jeremy, T.1 aMaghrebi, Mohammad, F.1 aCarmichael, Howard1 aGorshkov, Alexey, V.1 aFoss-Feig, Michael uhttps://arxiv.org/abs/2006.0559302329nas a2200157 4500008004100000245005700041210005600098260001400154490000700168520186200175100002202037700002502059700002302084700002702107856003702134 2020 eng d00aNon-equilibrium fixed points of coupled Ising models0 aNonequilibrium fixed points of coupled Ising models c2/26/20200 v103 aDriven-dissipative systems can exhibit non-equilibrium phenomena that are absent in their equilibrium counterparts. However, phase transitions present in these systems generically exhibit an effectively classical equilibrium behavior in spite of their quantum non-equilibrium origin. In this paper, we show that multicritical points in driven-dissipative systems can give rise to genuinely non-equilibrium behavior. We investigate a non-equilibrium driven-dissipative model of interacting bosons that exhibits two distinct phase transitions: one from a high- to a low-density phase---reminiscent of a liquid-gas transition---and another to an antiferromagnetic phase. Each phase transition is described by the Ising universality class characterized by an (emergent or microscopic) Z2 symmetry. They, however, coalesce at a multicritical point giving rise to a non-equilibrium model of coupled Ising-like order parameters described by a Z2×Z2 symmetry. Using a dynamical renormalization-group approach, we show that a pair of non-equilibrium fixed points (NEFPs) emerge that govern the long-distance critical behavior of the system. We elucidate various exotic features of these NEFPs. In particular, we show that a generic continuous scale invariance at criticality is reduced to a discrete scale invariance. This further results in complex-valued critical exponents, spiraling phase boundaries, and a complex Liouvillian gap even close to the phase transition. As direct evidence of the non-equilibrium nature of the NEFPs, we show that the fluctuation-dissipation relation is violated at all scales, leading to an effective temperature that becomes "hotter" and "hotter" at longer and longer wavelengths. Finally, we argue that this non-equilibrium behavior can be observed in cavity arrays with cross-Kerr nonlinearities.
1 aYoung, Jeremy, T.1 aGorshkov, Alexey, V.1 aFoss-Feig, Michael1 aMaghrebi, Mohammad, F. uhttps://arxiv.org/abs/1903.0256901741nas a2200205 4500008004100000245007000041210006900111260001500180490000600195520112800201100001901329700002001348700001301368700002401381700002201405700002301427700002301450700002501473856003701498 2019 eng d00aLocality and digital quantum simulation of power-law interactions0 aLocality and digital quantum simulation of powerlaw interactions c07/10/20190 v93 aThe propagation of information in non-relativistic quantum systems obeys a speed limit known as a Lieb-Robinson bound. We derive a new Lieb-Robinson bound for systems with interactions that decay with distance r as a power law, 1/rα. The bound implies an effective light cone tighter than all previous bounds. Our approach is based on a technique for approximating the time evolution of a system, which was first introduced as part of a quantum simulation algorithm by Haah et al. [arXiv:1801.03922]. To bound the error of the approximation, we use a known Lieb-Robinson bound that is weaker than the bound we establish. This result brings the analysis full circle, suggesting a deep connection between Lieb-Robinson bounds and digital quantum simulation. In addition to the new Lieb-Robinson bound, our analysis also gives an error bound for the Haah et al. quantum simulation algorithm when used to simulate power-law decaying interactions. In particular, we show that the gate count of the algorithm scales with the system size better than existing algorithms when α>3D (where D is the number of dimensions).
1 aTran, Minh, C.1 aGuo, Andrew, Y.1 aSu, Yuan1 aGarrison, James, R.1 aEldredge, Zachary1 aFoss-Feig, Michael1 aChilds, Andrew, M.1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1808.0522501425nas a2200157 4500008004100000245007800041210006900119260001500188520092400203100001601127700001701143700002201160700002501182700002301207856003701230 2018 eng d00aDistributed Quantum Metrology and the Entangling Power of Linear Networks0 aDistributed Quantum Metrology and the Entangling Power of Linear c2018/07/253 aWe derive a bound on the ability of a linear optical network to estimate a linear combination of independent phase shifts by using an arbitrary non-classical but unentangled input state, thereby elucidating the quantum resources required to obtain the Heisenberg limit with a multi-port interferometer. Our bound reveals that while linear networks can generate highly entangled states, they cannot effectively combine quantum resources that are well distributed across multiple modes for the purposes of metrology: in this sense linear networks endowed with well-distributed quantum resources behave classically. Conversely, our bound shows that linear networks can achieve the Heisenberg limit for distributed metrology when the input photons are hoarded in a small number of input modes, and we present an explicit scheme for doing so. Our results also have implications for measures of non-classicality.
1 aGe, Wenchao1 aJacobs, Kurt1 aEldredge, Zachary1 aGorshkov, Alexey, V.1 aFoss-Feig, Michael uhttps://arxiv.org/abs/1707.0665501538nas a2200157 4500008004100000245007800041210006900119260001500188520103700203100001601240700001701256700002201273700002501295700002301320856003701343 2018 eng d00aDistributed Quantum Metrology and the Entangling Power of Linear Networks0 aDistributed Quantum Metrology and the Entangling Power of Linear c2018/07/253 aWe derive a bound on the ability of a linear optical network to estimate a linear combination of independent phase shifts by using an arbitrary non-classical but unentangled input state, thereby elucidating the quantum resources required to obtain the Heisenberg limit with a multi-port interferometer. Our bound reveals that while linear networks can generate highly entangled states, they cannot effectively combine quantum resources that are well distributed across multiple modes for the purposes of metrology: in this sense linear networks endowed with well-distributed quantum resources behave classically. Conversely, our bound shows that linear networks can achieve the Heisenberg limit for distributed metrology when the input photons are hoarded in a small number of input modes, and we present an explicit scheme for doing so. Our results also have implications for measures of non-classicality.
1 aGe, Wenchao1 aJacobs, Kurt1 aEldredge, Zachary1 aGorshkov, Alexey, V.1 aFoss-Feig, Michael uhttps://arxiv.org/abs/1707.0665512409nas a2200169 45000080041000002450055000412100055000963000047001514900008001985201188600206100002312092700002012115700001912135700002312154700002512177856003712202 2018 eng d00aDynamical phase transitions in sampling complexity0 aDynamical phase transitions in sampling complexity a12 pages, 4 figures. v3: published version0 v1213 aWe make the case for studying the complexity of approximately simulating (sampling) quantum systems for reasons beyond that of quantum computational supremacy, such as diagnosing phase transitions. We consider the sampling complexity as a function of time t due to evolution generated by spatially local quadratic bosonic Hamiltonians. We obtain an upper bound on the scaling of t with the number of bosons n for which approximate sampling is classically efficient. We also obtain a lower bound on the scaling of t with n for which any instance of the boson sampling problem reduces to this problem and hence implies that the problem is hard, assuming the conjectures of Aaronson and Arkhipov [Proc. 43rd Annu. ACM Symp. Theory Comput. STOC '11]. This establishes a dynamical phase transition in sampling complexity. Further, we show that systems in the Anderson-localized phase are always easy to sample from at arbitrarily long times. We view these results in the light of classifying phases of physical systems based on parameters in the Hamiltonian. In doing so, we combine ideas from mathematical physics and computational complexity to gain insight into the behavior of condensed matter, atomic, molecular and optical systems.
1 aDeshpande, Abhinav1 aFefferman, Bill1 aTran, Minh, C.1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1703.0533201192nas a2200145 4500008004100000245007300041210006900114260001500183520071800198100002200916700002300938700002400961700002500985856003601010 2018 eng d00aOptimal and Secure Measurement Protocols for Quantum Sensor Networks0 aOptimal and Secure Measurement Protocols for Quantum Sensor Netw c2018/03/233 aStudies of quantum metrology have shown that the use of many-body entangled states can lead to an enhancement in sensitivity when compared to product states. In this paper, we quantify the metrological advantage of entanglement in a setting where the quantity to be measured is a linear function of parameters coupled to each qubit individually. We first generalize the Heisenberg limit to the measurement of non-local observables in a quantum network, deriving a bound based on the multi-parameter quantum Fisher information. We then propose a protocol that can make use of GHZ states or spin-squeezed states, and show that in the case of GHZ states the procedure is optimal, i.e., it saturates our bound.
1 aEldredge, Zachary1 aFoss-Feig, Michael1 aRolston, Steven, L.1 aGorshkov, Alexey, V. uhttp://arxiv.org/abs/1607.0464605805nas a2200145 4500008004100000245004900041210004900090260001500139520537700154100002305531700002005554700002305574700002505597856003705622 2017 eng d00aComplexity of sampling as an order parameter0 aComplexity of sampling as an order parameter c2017/03/153 aWe consider the classical complexity of approximately simulating time evolution under spatially local quadratic bosonic Hamiltonians for time t. We obtain upper and lower bounds on the scaling of twith the number of bosons, n, for which simulation, cast as a sampling problem, is classically efficient and provably hard, respectively. We view these results in the light of classifying phases of physical systems based on parameters in the Hamiltonian and conjecture a link to dynamical phase transitions. In doing so, we combine ideas from mathematical physics and computational complexity to gain insight into the behavior of condensed matter systems.
1 aDeshpande, Abhinav1 aFefferman, Bill1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1703.0533201217nas 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/1702.0536802145nas a2200205 4500008004100000245005800041210005700099260001500156300001100171490000700182520152100189100002301710700002101733700002201754700002101776700002501797700002101822700002701843856006901870 2017 eng d00aEmergent equilibrium in many-body optical bistability0 aEmergent equilibrium in manybody optical bistability c2017/04/17 a0438260 v953 aMany-body systems constructed of quantum-optical building blocks can now be realized in experimental platforms ranging from exciton-polariton fluids to ultracold gases of Rydberg atoms, establishing a fascinating interface between traditional many-body physics and the driven-dissipative, non-equilibrium setting of cavity-QED. At this interface, the standard techniques and intuitions of both fields are called into question, obscuring issues as fundamental as the role of fluctuations, dimensionality, and symmetry on the nature of collective behavior and phase transitions. Here, we study the driven-dissipative Bose-Hubbard model, a minimal description of numerous atomic, optical, and solid-state systems in which particle loss is countered by coherent driving. Despite being a lattice version of optical bistability---a foundational and patently non-equilibrium model of cavity-QED---the steady state possesses an emergent equilibrium description in terms of a classical Ising model. We establish this picture by identifying a limit in which the quantum dynamics is asymptotically equivalent to non-equilibrium Langevin equations, which support a phase transition described by model A of the Hohenberg-Halperin classification. Numerical simulations of the Langevin equations corroborate this picture, producing results consistent with the behavior of a finite-temperature Ising model.
1 aFoss-Feig, Michael1 aNiroula, Pradeep1 aYoung, Jeremy, T.1 aHafezi, Mohammad1 aGorshkov, Alexey, V.1 aWilson, Ryan, M.1 aMaghrebi, Mohammad, F. uhttps://journals.aps.org/pra/abstract/10.1103/PhysRevA.95.04382602985nas a2200157 4500008004100000245004900041210004900090260001500139300001100154490000700165520255000172100002002722700002302742700002502765856003702790 2017 eng d00aExact sampling hardness of Ising spin models0 aExact sampling hardness of Ising spin models c2017/09/14 a0323240 v963 aWe study the complexity of classically sampling from the output distribution of an Ising spin model, which can be implemented naturally in a variety of atomic, molecular, and optical systems. In particular, we construct a specific example of an Ising Hamiltonian that, after time evolution starting from a trivial initial state, produces a particular output configuration with probability very nearly proportional to the square of the permanent of a matrix with arbitrary integer entries. In a similar spirit to boson sampling, the ability to sample classically from the probability distribution induced by time evolution under this Hamiltonian would imply unlikely complexity theoretic consequences, suggesting that the dynamics of such a spin model cannot be efficiently simulated with a classical computer. Physical Ising spin systems capable of achieving problem-size instances (i.e., qubit numbers) large enough so that classical sampling of the output distribution is classically difficult in practice may be achievable in the near future. Unlike boson sampling, our current results only imply hardness of exact classical sampling, leaving open the important question of whether a much stronger approximate-sampling hardness result holds in this context. The latter is most likely necessary to enable a convincing experimental demonstration of quantum supremacy. As referenced in a recent paper [A. Bouland, L. Mancinska, and X. Zhang, in Proceedings of the 31st Conference on Computational Complexity (CCC 2016), Leibniz International Proceedings in Informatics (Schloss Dagstuhl–Leibniz-Zentrum für Informatik, Dagstuhl, 2016)], our result completes the sampling hardness classification of two-qubit commuting Hamiltonians.
1 aFefferman, Bill1 aFoss-Feig, Michael1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1701.0316727528nas 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/1612.0244201534nas a2200169 4500008004100000245006200041210005800103260001500161490000800176520102300184100002301207700002201230700002301252700002501275700002701300856003701327 2017 eng d00aA solvable family of driven-dissipative many-body systems0 asolvable family of drivendissipative manybody systems c2017/11/100 v1193 aExactly solvable models have played an important role in establishing the sophisticated modern understanding of equilibrium many-body physics. And conversely, the relative scarcity of solutions for non-equilibrium models greatly limits our understanding of systems away from thermal equilibrium. We study a family of nonequilibrium models, some of which can be viewed as dissipative analogues of the transverse-field Ising model, in that an effectively classical Hamiltonian is frustrated by dissipative processes that drive the system toward states that do not commute with the Hamiltonian. Surprisingly, a broad and experimentally relevant subset of these models can be solved efficiently in any number of spatial dimensions. We leverage these solutions to prove a no-go theorem on steady-state phase transitions in a many-body model that can be realized naturally with Rydberg atoms or trapped ions, and to compute the effects of decoherence on a canonical trapped-ion-based quantum computation architecture.
1 aFoss-Feig, Michael1 aYoung, Jeremy, T.1 aAlbert, Victor, V.1 aGorshkov, Alexey, V.1 aMaghrebi, Mohammad, F. uhttps://arxiv.org/abs/1703.0462600514nas 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/1508.0090601682nas a2200193 4500008004100000245006100041210006100102260001500163300001100178490000700189520113200196100002101328700002101349700001301370700002501383700002101408700002301429856003601452 2016 eng d00aCollective phases of strongly interacting cavity photons0 aCollective phases of strongly interacting cavity photons c2016/09/01 a0338010 v943 aWe study a coupled array of coherently driven photonic cavities, which maps onto a driven-dissipative XY spin-12 model with ferromagnetic couplings in the limit of strong optical nonlinearities. Using a site-decoupled mean-field approximation, we identify steady state phases with canted antiferromagnetic order, in addition to limit cycle phases, where oscillatory dynamics persist indefinitely. We also identify collective bistable phases, where the system supports two steady states among spatially uniform, antiferromagnetic, and limit cycle phases. We compare these mean-field results to exact quantum trajectories simulations for finite one-dimensional arrays. The exact results exhibit short-range antiferromagnetic order for parameters that have significant overlap with the mean-field phase diagram. In the mean-field bistable regime, the exact quantum dynamics exhibits real-time collective switching between macroscopically distinguishable states. We present a clear physical picture for this dynamics, and establish a simple relationship between the switching times and properties of the quantum Liouvillian.
1 aWilson, Ryan, M.1 aMahmud, Khan, W.1 aHu, Anzi1 aGorshkov, Alexey, V.1 aHafezi, Mohammad1 aFoss-Feig, Michael uhttp://arxiv.org/abs/1601.0685701507nas 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/1505.0314601656nas a2200193 4500008004100000245007500041210006900116260001500185300001400200490000800214520108600222100001801308700001501326700001901341700002401360700002301384700001801407856003701425 2015 eng d00a2D Superexchange mediated magnetization dynamics in an optical lattice0 a2D Superexchange mediated magnetization dynamics in an optical l c2015/04/30 a540 - 5440 v3483 a The competition of magnetic exchange interactions and tunneling underlies
many complex quantum phenomena observed in real materials. We study
non-equilibrium magnetization dynamics in an extended 2D system by loading
effective spin-1/2 bosons into a spin-dependent optical lattice, and we use the
lattice to separately control the resonance conditions for tunneling and
superexchange. After preparing a non-equilibrium anti-ferromagnetically ordered
state, we observe relaxation dynamics governed by two well-separated rates,
which scale with the underlying Hamiltonian parameters associated with
superexchange and tunneling. Remarkably, with tunneling off-resonantly
suppressed, we are able to observe superexchange dominated dynamics over two
orders of magnitude in magnetic coupling strength, despite the presence of
vacancies. In this regime, the measured timescales are in agreement with simple
theoretical estimates, but the detailed dynamics of this 2D, strongly
correlated, and far-from-equilibrium quantum system remain out of reach of
current computational techniques.
1 aBrown, R., C.1 aWyllie, R.1 aKoller, S., B.1 aGoldschmidt, E., A.1 aFoss-Feig, Michael1 aPorto, J., V. uhttp://arxiv.org/abs/1411.7036v102223nas a2200193 4500008004100000245007100041210006900112260001500181300001200196490000800208520166400216100002001880700001901900700002301919700001701942700001601959700001801975856003601993 2015 eng d00aEntangling two transportable neutral atoms via local spin exchange0 aEntangling two transportable neutral atoms via local spin exchan c2015/11/02 a208-2110 v5273 a To advance quantum information science a constant pursuit is the search for
physical systems that meet the stringent requirements for creating and
preserving quantum entanglement. In atomic physics, robust two-qubit
entanglement is typically achieved by strong, long-range interactions in the
form of Coulomb interactions between ions or dipolar interactions between
Rydberg atoms. While these interactions allow fast gates, atoms subject to
these interactions must overcome the associated coupling to the environment and
cross-talk among qubits. Local interactions, such as those requiring
significant wavefunction overlap, can alleviate these detrimental effects yet
present a new challenge: To distribute entanglement, qubits must be
transported, merged for interaction, and then isolated for storage and
subsequent operations. Here we show how, via a mobile optical tweezer, it is
possible to prepare and locally entangle two ultracold neutral atoms, and then
separate them while preserving their entanglement. While ultracold neutral atom
experiments have measured dynamics consistent with spin entanglement, we are
now able to demonstrate two-particle coherence via application of a local
gradient and parity measurements; this new entanglement-verification protocol
could be applied to arbitrary spin-entangled states of spatially-separated
atoms. The local entangling operation is achieved via ultracold spin-exchange
interactions, and quantum tunneling is used to combine and separate atoms. Our
toolset provides a framework for dynamically entangling remote qubits via local
operations within a large-scale quantum register.
1 aKaufman, A., M.1 aLester, B., J.1 aFoss-Feig, Michael1 aWall, M., L.1 aRey, A., M.1 aRegal, C., A. uhttp://arxiv.org/abs/1507.0558601522nas 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/1410.3466v101571nas a2200217 4500008004100000245007400041210006900115260001500184300001400199490000800213520093800221100002001159700001901179700002101198700001701219700002301236700002301259700001601282700001801298856003701316 2014 eng d00aHong-Ou-Mandel atom interferometry in tunnel-coupled optical tweezers0 aHongOuMandel atom interferometry in tunnelcoupled optical tweeze c2014/06/26 a306 - 3090 v3453 a The quantum statistics of atoms is typically observed in the behavior of an
ensemble via macroscopic observables. However, quantum statistics modifies the
behavior of even two particles, inducing remarkable consequences that are at
the heart of quantum science. Here we demonstrate near-complete control over
all the internal and external degrees of freedom of two laser-cooled 87Rb atoms
trapped in two optical tweezers. This full controllability allows us to
implement a massive-particle analog of a Hong-Ou-Mandel interferometer where
atom tunneling plays the role of a photon beamsplitter. We use the
interferometer to probe the effect of quantum statistics on the two-atom
dynamics under tunable initial conditions, chosen to adjust the degree of
atomic indistinguishability. Our work thereby establishes laser-cooled atoms in
optical tweezers as a new route to bottom-up engineering of scalable,
low-entropy quantum systems.
1 aKaufman, A., M.1 aLester, B., J.1 aReynolds, C., M.1 aWall, M., L.1 aFoss-Feig, Michael1 aHazzard, K., R. A.1 aRey, A., M.1 aRegal, C., A. uhttp://arxiv.org/abs/1312.7182v202029nas a2200241 4500008004100000245006600041210006500107260001400172490000800186520133800194100002601532700001801558700002301576700001201599700002201611700002101633700002001654700002301674700001201697700002101709700002001730856003701750 2014 eng d00aMany-body dynamics of dipolar molecules in an optical lattice0 aManybody dynamics of dipolar molecules in an optical lattice c2014/11/70 v1133 a Understanding the many-body dynamics of isolated quantum systems is one of
the central challenges in modern physics. To this end, the direct experimental
realization of strongly correlated quantum systems allows one to gain insights
into the emergence of complex phenomena. Such insights enable the development
of theoretical tools that broaden our understanding. Here, we theoretically
model and experimentally probe with Ramsey spectroscopy the quantum dynamics of
disordered, dipolar-interacting, ultracold molecules in a partially filled
optical lattice. We report the capability to control the dipolar interaction
strength, and we demonstrate that the many-body dynamics extends well beyond a
nearest-neighbor or mean-field picture, and cannot be quantitatively described
using previously available theoretical tools. We develop a novel cluster
expansion technique and demonstrate that our theoretical method accurately
captures the measured dependence of the spin dynamics on molecule number and on
the dipolar interaction strength. In the spirit of quantum simulation, this
agreement simultaneously benchmarks the new theoretical method and verifies our
microscopic understanding of the experiment. Our findings pave the way for
numerous applications in quantum information science, metrology, and condensed
matter physics.
1 aHazzard, Kaden, R. A.1 aGadway, Bryce1 aFoss-Feig, Michael1 aYan, Bo1 aMoses, Steven, A.1 aCovey, Jacob, P.1 aYao, Norman, Y.1 aLukin, Mikhail, D.1 aYe, Jun1 aJin, Deborah, S.1 aRey, Ana, Maria uhttp://arxiv.org/abs/1402.2354v102028nas 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/1401.6174v201850nas a2200205 4500008004100000245008200041210006900123260001500192490000700207520120600214100002601420700002601446700002301472700002701495700002701522700001701549700002101566700002001587856003701607 2014 eng d00aQuantum correlations and entanglement in far-from-equilibrium spin systems
0 aQuantum correlations and entanglement in farfromequilibrium spin c2014/12/150 v903 a By applying complementary analytic and numerical methods, we investigate the
dynamics of spin-$1/2$ XXZ models with variable-range interactions in arbitrary
dimensions. The dynamics we consider is initiated from uncorrelated states that
are easily prepared in experiments, and can be equivalently viewed as either
Ramsey spectroscopy or a quantum quench. Our primary focus is the dynamical
emergence of correlations and entanglement in these far-from-equilibrium
interacting quantum systems: we characterize these correlations by the
entanglement entropy, concurrence, and squeezing, which are inequivalent
measures of entanglement corresponding to different quantum resources. In one
spatial dimension, we show that the time evolution of correlation functions
manifests a non-perturbative dynamic singularity. This singularity is
characterized by a universal power-law exponent that is insensitive to small
perturbations. Explicit realizations of these models in current experiments
using polar molecules, trapped ions, Rydberg atoms, magnetic atoms, and
alkaline-earth and alkali atoms in optical lattices, along with the relative
merits and limitations of these different systems, are discussed.
1 aHazzard, Kaden, R. A.1 avan den Worm, Mauritz1 aFoss-Feig, Michael1 aManmana, Salvatore, R.1 aTorre, Emanuele, Dalla1 aPfau, Tilman1 aKastner, Michael1 aRey, Ana, Maria uhttp://arxiv.org/abs/1406.0937v102020nas a2200265 4500008004100000245009000041210006900131260001400200490000800214520123900222100001501461700001801476700002301494700002801517700001801545700002601563700001201589700002201601700002101623700002101644700001201665700002001677700002001697856003701717 2014 eng d00aSuppressing the loss of ultracold molecules via the continuous quantum Zeno effect
0 aSuppressing the loss of ultracold molecules via the continuous q c2014/2/200 v1123 a We investigate theoretically the suppression of two-body losses when the
on-site loss rate is larger than all other energy scales in a lattice. This
work quantitatively explains the recently observed suppression of chemical
reactions between two rotational states of fermionic KRb molecules confined in
one-dimensional tubes with a weak lattice along the tubes [Yan et al., Nature
501, 521-525 (2013)]. New loss rate measurements performed for different
lattice parameters but under controlled initial conditions allow us to show
that the loss suppression is a consequence of the combined effects of lattice
confinement and the continuous quantum Zeno effect. A key finding, relevant for
generic strongly reactive systems, is that while a single-band theory can
qualitatively describe the data, a quantitative analysis must include multiband
effects. Accounting for these effects reduces the inferred molecule filling
fraction by a factor of five. A rate equation can describe much of the data,
but to properly reproduce the loss dynamics with a fixed filling fraction for
all lattice parameters we develop a mean-field model and benchmark it with
numerically exact time-dependent density matrix renormalization group
calculations.
1 aZhu, Bihui1 aGadway, Bryce1 aFoss-Feig, Michael1 aSchachenmayer, Johannes1 aWall, Michael1 aHazzard, Kaden, R. A.1 aYan, Bo1 aMoses, Steven, A.1 aCovey, Jacob, P.1 aJin, Deborah, S.1 aYe, Jun1 aHolland, Murray1 aRey, Ana, Maria uhttp://arxiv.org/abs/1310.2221v202138nas a2200181 4500008004100000245011400041210006900155260001500224300001100239490000700250520155000257100002301807700002401830700002301854700002001877700002201897856003701919 2013 eng d00aDynamical quantum correlations of Ising models on an arbitrary lattice and their resilience to decoherence
0 aDynamical quantum correlations of Ising models on an arbitrary l c2013/11/07 a1130080 v153 a Ising models, and the physical systems described by them, play a central role
in generating entangled states for use in quantum metrology and quantum
information. In particular, ultracold atomic gases, trapped ion systems, and
Rydberg atoms realize long-ranged Ising models, which even in the absence of a
transverse field can give rise to highly non-classical dynamics and long-range
quantum correlations. In the first part of this paper, we present a detailed
theoretical framework for studying the dynamics of such systems driven (at time
t=0) into arbitrary unentangled non-equilibrium states, thus greatly extending
and unifying the work of Ref. [1]. Specifically, we derive exact expressions
for closed-time-path ordered correlation functions, and use these to study
experimentally relevant observables, e.g. Bloch vector and spin-squeezing
dynamics. In the second part, these correlation functions are then used to
derive closed-form expressions for the dynamics of arbitrary spin-spin
correlation functions in the presence of both T_1 (spontaneous spin
relaxation/excitation) and T_2 (dephasing) type decoherence processes. Even
though the decoherence is local, our solution reveals that the competition
between Ising dynamics and T_1 decoherence gives rise to an emergent non-local
dephasing effect, thereby drastically amplifying the degradation of quantum
correlations. In addition to identifying the mechanism of this deleterious
effect, our solution points toward a scheme to eliminate it via
measurement-based coherent feedback.
1 aFoss-Feig, Michael1 aHazzard, Kaden, R A1 aBollinger, John, J1 aRey, Ana, Maria1 aClark, Charles, W uhttp://arxiv.org/abs/1306.0172v101291nas a2200157 4500008004100000245007400041210006900115260001400184490000800198520079400206100002601000700002701026700002301053700002001076856003701096 2013 eng d00aFar from equilibrium quantum magnetism with ultracold polar molecules0 aFar from equilibrium quantum magnetism with ultracold polar mole c2013/2/110 v1103 a Recent theory has indicated how to emulate tunable models of quantum
magnetism with ultracold polar molecules. Here we show that present molecule
optical lattice experiments can accomplish three crucial goals for quantum
emulation, despite currently being well below unit filling and not quantum
degenerate. The first is to verify and benchmark the models proposed to
describe these systems. The second is to prepare correlated and possibly useful
states in well-understood regimes. The third is to explore many-body physics
inaccessible to existing theoretical techniques. Our proposal relies on a
non-equilibrium protocol that can be viewed either as Ramsey spectroscopy or an
interaction quench. It uses only routine experimental tools available in any
ultracold molecule experiment.
1 aHazzard, Kaden, R. A.1 aManmana, Salvatore, R.1 aFoss-Feig, Michael1 aRey, Ana, Maria uhttp://arxiv.org/abs/1209.4076v101346nas a2200157 4500008004100000245008400041210006900125260001300194490000700207520084400214100002301058700002601081700002401107700002001131856003701151 2013 eng d00aNon-equilibrium dynamics of Ising models with decoherence: an exact solution
0 aNonequilibrium dynamics of Ising models with decoherence an exac c2013/4/30 v873 a The interplay between interactions and decoherence in many-body systems is of
fundamental importance in quantum physics: Decoherence can degrade
correlations, but can also give rise to a variety of rich dynamical and
steady-state behaviors. We obtain an exact analytic solution for the
non-equilibrium dynamics of Ising models with arbitrary interactions and
subject to the most general form of local Markovian decoherence. Our solution
shows that decoherence affects the relaxation of observables more than
predicted by single-particle considerations. It also reveals a dynamical phase
transition, specifically a Hopf bifurcation, which is absent at the
single-particle level. These calculations are applicable to ongoing quantum
information and emulation efforts using a variety of atomic, molecular,
optical, and solid-state systems.
1 aFoss-Feig, Michael1 aHazzard, Kaden, R. A.1 aBollinger, John, J.1 aRey, Ana, Maria uhttp://arxiv.org/abs/1209.5795v201519nas a2200217 4500008004100000245008300041210006900124260001400193490000800207520087700215100002001092700002101112700002201133700001201155700002101167700002301188700002001211700002101231700001201252856003701264 2012 eng d00aLong-lived dipolar molecules and Feshbach molecules in a 3D optical lattice
0 aLonglived dipolar molecules and Feshbach molecules in a 3D optic c2012/2/230 v1083 a We have realized long-lived ground-state polar molecules in a 3D optical
lattice, with a lifetime of up to 25 s, which is limited only by off-resonant
scattering of the trapping light. Starting from a 2D optical lattice, we
observe that the lifetime increases dramatically as a small lattice potential
is added along the tube-shaped lattice traps. The 3D optical lattice also
dramatically increases the lifetime for weakly bound Feshbach molecules. For a
pure gas of Feshbach molecules, we observe a lifetime of >20 s in a 3D optical
lattice; this represents a 100-fold improvement over previous results. This
lifetime is also limited by off-resonant scattering, the rate of which is
related to the size of the Feshbach molecule. Individually trapped Feshbach
molecules in the 3D lattice can be converted to pairs of K and Rb atoms and
back with nearly 100% efficiency.
1 aChotia, Amodsen1 aNeyenhuis, Brian1 aMoses, Steven, A.1 aYan, Bo1 aCovey, Jacob, P.1 aFoss-Feig, Michael1 aRey, Ana, Maria1 aJin, Deborah, S.1 aYe, Jun uhttp://arxiv.org/abs/1110.4420v101233nas a2200157 4500008004100000245006500041210006300106260001400169490000800183520075800191100002300949700002200972700002400994700002001018856003701038 2012 eng d00aSteady-state many-body entanglement of hot reactive fermions0 aSteadystate manybody entanglement of hot reactive fermions c2012/12/40 v1093 a Entanglement is typically created via systematic intervention in the time
evolution of an initially unentangled state, which can be achieved by coherent
control, carefully tailored non-demolition measurements, or dissipation in the
presence of properly engineered reservoirs. In this paper we show that
two-component Fermi gases at ~\mu K temperatures naturally evolve, in the
presence of reactive two-body collisions, into states with highly entangled
(Dicke-type) spin wavefunctions. The entanglement is a steady-state property
that emerges---without any intervention---from uncorrelated initial states, and
could be used to improve the accuracy of spectroscopy in experiments with
fermionic alkaline earth atoms or fermionic groundstate molecules.
1 aFoss-Feig, Michael1 aDaley, Andrew, J.1 aThompson, James, K.1 aRey, Ana, Maria uhttp://arxiv.org/abs/1207.4741v101461nas a2200133 4500008004100000245005000041210004900091260001500140490000700155520108500162100002301247700002001270856003701290 2011 eng d00aPhase diagram of the Bose Kondo-Hubbard model0 aPhase diagram of the Bose KondoHubbard model c2011/11/160 v843 a We study a bosonic version of the Kondo lattice model with an on-site
repulsion in the conduction band, implemented with alkali atoms in two bands of
an optical lattice. Using both weak and strong-coupling perturbation theory, we
find that at unit filling of the conduction bosons the superfluid to Mott
insulator transition should be accompanied by a magnetic transition from a
ferromagnet (in the superfluid) to a paramagnet (in the Mott insulator).
Furthermore, an analytic treatment of Gutzwiller mean-field theory reveals that
quantum spin fluctuations induced by the Kondo exchange cause the otherwise
continuous superfluid to Mott-insulator phase transition to be first order. We
show that lattice separability imposes a serious constraint on proposals to
exploit excited bands for quantum simulations, and discuss a way to overcome
this constraint in the context of our model by using an experimentally realized
non-separable lattice. A method to probe the first-order nature of the
transition based on collapses and revivals of the matter-wave field is also
discussed.
1 aFoss-Feig, Michael1 aRey, Ana, Maria uhttp://arxiv.org/abs/1103.0245v201646nas a2200157 4500008004100000245004100041210004100082260001500123490000700138520122200145100002301367700002101390700002001411700002001431856003701451 2010 eng d00aHeavy fermions in an optical lattice0 aHeavy fermions in an optical lattice c2010/11/220 v823 a We employ a mean-field theory to study ground-state properties and transport
of a two-dimensional gas of ultracold alklaline-earth metal atoms governed by
the Kondo Lattice Hamiltonian plus a parabolic confining potential. In a
homogenous system this mean-field theory is believed to give a qualitatively
correct description of heavy fermion metals and Kondo insulators: it reproduces
the Kondo-like scaling of the quasiparticle mass in the former, and the same
scaling of the excitation gap in the latter. In order to understand
ground-state properties in a trap we extend this mean-field theory via
local-density approximation. We find that the Kondo insulator gap manifests as
a shell structure in the trapped density profile. In addition, a strong
signature of the large Fermi surface expected for heavy fermion systems
survives the confinement, and could be probed in time-of-flight experiments.
From a full self-consistent diagonalization of the mean-field theory we are
able to study dynamics in the trap. We find that the mass enhancement of
quasiparticle excitations in the heavy Fermi liquid phase manifests as slowing
of the dipole oscillations that result from a sudden displacement of the trap
center.
1 aFoss-Feig, Michael1 aHermele, Michael1 aGurarie, Victor1 aRey, Ana, Maria uhttp://arxiv.org/abs/1007.5083v100925nas a2200145 4500008004100000245006200041210006200103260001300165490000700178520049300185100002300678700002100701700002000722856003700742 2010 eng d00aProbing the Kondo Lattice Model with Alkaline Earth Atoms0 aProbing the Kondo Lattice Model with Alkaline Earth Atoms c2010/5/70 v813 a We study transport properties of alkaline-earth atoms governed by the Kondo
Lattice Hamiltonian plus a harmonic confining potential, and suggest simple
dynamical probes of several different regimes of the phase diagram that can be
implemented with current experimental techniques. In particular, we show how
Kondo physics at strong coupling, low density, and in the heavy fermion phase
is manifest in the dipole oscillations of the conduction band upon displacement
of the trap center.
1 aFoss-Feig, Michael1 aHermele, Michael1 aRey, Ana, Maria uhttp://arxiv.org/abs/0912.4762v101016nas a2200145 4500008004100000245015100041210006900192260001500261300001000276490000700286520049000293100002300783700002700806856003700833 2009 eng d00aGeometric-Phase-Effect Tunnel-Splitting Oscillations in Single-Molecule Magnets with Fourth-Order Anisotropy Induced by Orthorhombic Distortion
0 aGeometricPhaseEffect TunnelSplitting Oscillations in SingleMolec c2009/04/30 a270020 v863 a We analyze the interference between tunneling paths that occurs for a spin
system with both fourth-order and second-order transverse anisotropy. Using an
instanton approach, we find that as the strength of the second-order transverse
anisotropy is increased, the tunnel splitting is modulated, with zeros
occurring periodically. This effect results from the interference of four
tunneling paths connecting easy-axis spin orientations and occurs in the
absence of any magnetic field.
1 aFoss-Feig, Michael1 aFriedman, Jonathan, R. uhttp://arxiv.org/abs/0809.2289v2