Recurrences in an isolated quantum many-body system

Rauer, Bernhard; Erne, Sebastian; Schweigler, Thomas; Cataldini, Federica; Tajik, Mohammadamin; Schmiedmayer, Jörg

doi:10.1126/science.aan7938

Cited by 102 publications

(172 citation statements)

References 53 publications

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“…was taken for a box-like longitudinal confinement [43] of 60 µm length. Matter-wave interferometry [44] gives access to the spatially resolved relative phase fluctuations ϕ x between the two superfluids.…”

Section: Experimental Results: Proof-of-principlementioning

confidence: 99%

“…Starting from the measured phase profiles, we can calculate the 1PI vertices in the same way as was done for the numerics (see section II and appendix C). For box like potentials one naturally gets Neumann boundary conditions (BC) for the phase from the condition of vanishing particle current on the edges [43]. From the cosine transform (compatible with the Neumann BC) of the complete system we therefore simply get the 1PI vertices of the Hamiltonian with this BC.…”

Section: Experimental Results: Proof-of-principlementioning

confidence: 99%

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Extracting the Field Theory Description of a Quantum Many-Body System from Experimental Data

et al. 2020

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Quantum field theory is a powerful tool to describe the relevant physics governing complex quantum many-body systems. Here we develop a general pathway to extract the irreducible building blocks of quantum field theoretical descriptions and its parameters purely from experimental data. This is accomplished by extracting the one-particle irreducible (1PI) vertices from which one can construct all observables. To match the capabilities of experimental techniques used in quantum simulation experiments, our approach employs a formulation of quantum field theory based on equal-time correlation functions only. We illustrate our procedure by applying it to the quantum sine-Gordon model in thermal equilibrium. The theoretical foundations are illustrated by estimating the irreducible vertices at equal times both analytically and using numerical simulations. We then demonstrate explicitly how to extract these quantities from an experiment where we quantum simulate the sine-Gordon model by two tunnel-coupled superfluids. We extract the full two-point function and the interaction vertex (four-point function) and their variation with momentum, encoding the 'running' of the couplings. The measured 1PI vertices are compared to the theoretical estimates, verifying our procedure. Our work opens new ways of addressing fundamental questions in quantum field theory, which are relevant in high-energy and condensed matter physics, and in taking quantum phenomena from fundamental science to practical technology. arXiv:1909.12815v1 [cond-mat.quant-gas]

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Section: Experimental Results: Proof-of-principlementioning

confidence: 99%

Section: Experimental Results: Proof-of-principlementioning

confidence: 99%

Extracting the Field Theory Description of a Quantum Many-Body System from Experimental Data

et al. 2020

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“…Moreover, for large N we demonstrated the emergence of nearly equidistant spectra giving rise to recurrences in OTOCs on log N -time scales, resembling features of time crystals [73]. Their observation should be in experimental reach since, e.g., recurrences based on stable dynamics have already been observed in a system with thousands of atoms [85]. Our analysis of the non-integrable 5-mode model shows that such memory effects do not require integrability and indicates their existence in larger classes of critical systems with a dynamical decoupling of a dominant unstable mode from other collective degrees of freedom.…”

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confidence: 87%

Reversible Quantum Information Spreading in Many-Body Systems near Criticality

et al. 2019

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Quantum chaotic interacting N -particle systems are assumed to show fast and irreversible spreading of quantum information on short (Ehrenfest) time scales ∼ log N . Here we show that, near criticality, certain many-body systems exhibit fast initial scrambling, followed subsequently by oscillatory behavior between reentrant localization and delocalization of information in Hilbert space. We consider both integrable and nonintegrable quantum critical bosonic systems with attractive contact interaction that exhibit locally unstable dynamics in the corresponding many-body phase space of the large-N limit. Semiclassical quantization of the latter accounts for many-body correlations in excellent agreement with simulations. Most notably, it predicts an asymptotically constant local level spacing /τ , again given by τ ∼ log N . This unique timescale governs the long-time behavior of out-of-time-order correlators that feature quasi-periodic recurrences indicating reversibility.The dynamics of quantum information in complex many-body (MB) systems presently attracts a lot of attention [1, 2] ranging from atomic and condensed quantum matter to high energy physics. The evolution of an (excited) quantum MB system towards a state of thermal equilibrium usually goes along with the scrambling of quantum correlations, encoded in the initial state, across the system's many degrees of freedom. Such dynamics requires an improved understanding of MB quantum chaos and the link with thermalization [3-6] and its suppression [1,7,8].Echo protocols, measuring how a perturbation affects successive forward and backward propagations in time, sensitively probe the stability of complex quantum dynamics. Here, out-of-time-order correlators (OTOCs) [9-11]play a central role, with first experimental implementations [12-14], allowing to distinguish various classes of MB systems by their operator growth. On the one side there are slow scramblers, such as systems in the MB localized phase exhibiting logarithmically slow operator spreading [15-18] or, e.g., Luttinger liquids [19] showing only quadratic increase. On the other side, an exponentially fast initial growth of OTOCs is commonly viewed as a quantum signature of MB chaos. Examples comprise systems with holographic duals to black holes [10,20], the SYK-model [11,[21][22][23], and condensed matter systems close to a quantum phase transition (QPT) [24][25][26][27] or exhibiting chaos in the classical limit of large particle number N . In such large-N systems, the exponential growth rate for OTOCs is given by the Lyapunov exponent of their classical counterpart [10,[27][28][29][30][31][32][33][34] and prevails up to the Ehrenfest log N time where MB quantum interference sets in [32,35]. Subsequent OTOC time evolution towards an ergodic limit is then often governed by slow classical modes [36].Here we show that exponentially fast scrambling need not necessarily lead to quantum information loss: There exist systems exhibiting initial growth of complexity without relaxation, i.e., after a quench to ...

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“…(iii) We have neglected interactions between the bath modes, which is an excellent approximation even in the condensed regime, where the excitations are well-described by non-interacting Bogoliubov modes [51,54]. We note, however, that these interactions must be included in a fully quantitative study of the thermalization dynamics, which is beyond the scope of this paper.…”

Section: Model Limitationsmentioning

confidence: 99%

Quantized refrigerator for an atomic cloud

Niedenzu

Mazets

Kurizki

et al. 2019

Quantum

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We propose to implement a quantized thermal machine based on a mixture of two atomic species. One atomic species implements the working medium and the other implements two (cold and hot) baths. We show that such a setup can be employed for the refrigeration of a large bosonic cloud starting above and ending below the condensation threshold. We analyze its operation in a regime conforming to the quantized Otto cycle and discuss the prospects for continuous-cycle operation, addressing the experimental as well as theoretical limitations. Beyond its applicative significance, this setup has a potential for the study of fundamental questions of quantum thermodynamics.Accepted in Quantum 2019-06-13, click title to verify arXiv:1812.08474v3 [quant-ph]

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Recurrences in an isolated quantum many-body system

Cited by 102 publications

References 53 publications

Extracting the Field Theory Description of a Quantum Many-Body System from Experimental Data

Extracting the Field Theory Description of a Quantum Many-Body System from Experimental Data

Reversible Quantum Information Spreading in Many-Body Systems near Criticality

Quantized refrigerator for an atomic cloud

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