BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Samuel Garratt (Oxford University) DTSTART:20200917T150000Z DTEND:20200917T160000Z DTSTAMP:20260404T111412Z UID:QChaos2020/1 DESCRIPTION:Title: Many-body quantum chaos and local pairing of Feynman histories\nby Samuel Garratt (Oxford University) as part of Quantum Chaos 2020 Se minars\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Adolfo del Campo (Donostia International Physics Center) DTSTART:20200924T150000Z DTEND:20200924T160000Z DTSTAMP:20260404T111412Z UID:QChaos2020/2 DESCRIPTION:Title: Quantum Chaos versus Decoherence\nby Adolfo del Campo (Donos tia International Physics Center) as part of Quantum Chaos 2020 Seminars\n \n\nAbstract\nQuantum chaos imposes universal spectral signatures that gov ern the thermofield dynamics of a many-body system in isolation. The fidel ity between the initial and time-evolving thermofield double states exhibi ts as a function of time a decay\, dip\, ramp and plateau. Sources of deco herence give rise to a non-unitary evolution and result in information los s. Energy dephasing gradually suppresses quantum noise fluctuations and th e dip associated with spectral correlations. Decoherence further delays th e appearance of the dip and shortens the span of the linear ramp associate d with chaotic behavior. The interplay between signatures of quantum chaos and information loss is determined by the competition among the decoheren ce\, dip and plateau characteristic times\, as demonstrated in the stochas tic Sachdev-Ye-Kitaev model.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Anabelle Bohrdt (Technical University Munich) DTSTART:20201001T150000Z DTEND:20201001T160000Z DTSTAMP:20260404T111412Z UID:QChaos2020/3 DESCRIPTION:Title: Probing dynamics in quantum simulators\nby Anabelle Bohrdt ( Technical University Munich) as part of Quantum Chaos 2020 Seminars\n\n\nA bstract\nIn this talk I will discuss new possibilities to probe the dynami cs of quantum many-body systems\, in particular the Bose-Hubbard model wit h and without disorder. \nOut-of-time-ordered (OTO) correlation functions have been proposed to describe the distribution or “scrambling” of inf ormation across a quantum state. We investigate both time-ordered and OTO correlation functions in the non-integrable\, one-dimensional Bose-Hubbard model at high temperatures where well-defined quasiparticles cease to exi st. We propose an interferometric scheme to approach the challenge of meas uring these correlation functions in real space and time. Performing numer ical simulations based on matrix product operators\, we observe a linear l ight-cone spreading of quantum information in the OTO correlators. In cont rast with the fast spreading of information\, the thermalization of the sy stem takes parametrically longer due to the slow diffusion of conserved qu antities. Adding strong disorder can inhibit thermalization\, leading to a many-body localized (MBL) phase. Beyond the absence of transport\, the MB L phase has distinctive signatures\, such as slow dephasing and logarithmi c entanglement growth. We experimentally probe these signatures in a syste m of coupled superconducting qubits.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Lennart Dabelow (Bielefeld University) DTSTART:20201008T150000Z DTEND:20201008T160000Z DTSTAMP:20260404T111412Z UID:QChaos2020/4 DESCRIPTION:Title: Typicality approach to perturbed quantum many-body relaxation\nby Lennart Dabelow (Bielefeld University) as part of Quantum Chaos 2020 Seminars\n\n\nAbstract\nWe develop an analytical prediction for the relax ation of isolated many-body quantum systems subject to weak-to-moderate pe rturbations. Provided that the unperturbed behavior is known\, we employ a typicality approach modeling the essential characteristics of the perturb ation operator to describe the time evolution of expectation values in the perturbed system. In particular\, the prediction identifies two decisive parameters of the perturbation: its overall strength and its energy range or band width. The theory provides a unified framework for such diverse ph enomena as prethermalization\, quantum quenches\, or the relaxation of sys tem-bath compounds. We demonstrate its wide applicability by comparison wi th various experimental and numerical examples.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Ranard (Stanford University) DTSTART:20201015T150000Z DTEND:20201015T160000Z DTSTAMP:20260404T111412Z UID:QChaos2020/5 DESCRIPTION:Title: Bounding the spread of quantum information\, and emergent classi cality in dynamics of large systems\nby Daniel Ranard (Stanford Univer sity) as part of Quantum Chaos 2020 Seminars\n\n\nAbstract\nHow can inform ation about a single subsystem spread through a many-body environment? We show that whenever a subsystem interacts with an environment\, for almost everywhere in the environment\, any locally accessible information about the subsystem must be approximately classical\, i.e. obtainable from some fixed measurement. The result strengthens the earlier result of arXiv:1310 .8640. It may also be seen as a new consequence of the principles of no-c loning or monogamy of entanglement. The proof offers a constructive optimi zation procedure for determining the effective "measurement" on the subsys tem induced by the dynamics. Alternatively\, under channel-state duality\, these results characterize the marginals of multipartite states. Talk ba sed primarily on arXiv:2001.01507.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Shreya Vardhan (MIT) DTSTART:20201022T150000Z DTEND:20201022T160000Z DTSTAMP:20260404T111412Z UID:QChaos2020/6 DESCRIPTION:Title: A universal approximation for entanglement entropies of equilibr ated pure states\nby Shreya Vardhan (MIT) as part of Quantum Chaos 202 0 Seminars\n\n\nAbstract\nWhen a pure state in a non-integrable quantum ma ny-body system is evolved to late times\, we expect it to thermalize—tha t is\, we expect its macroscopic properties to resemble those of an equili brium density matrix. However\, the entanglement entropies of such a state must obey certain constraints coming from unitarity\, which are not obeye d by an equilibrium density matrix. In this talk\, I will explain an appro ximation method that leads to a simple universal expression for the entang lement entropies of an equilibrated pure state in any quantum many-body sy stem. This expression is independent of the details of the initial state a nd hence reflects thermalization\, while also being manifestly consistent with unitarity. I will also discuss how this method can be applied to equi librated pure states in gravitational systems\, such as those involving bl ack holes\, where it can be used to address the information loss paradox o f Hawking.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Vedika Khemani (Stanford University) DTSTART:20201029T180000Z DTEND:20201029T190000Z DTSTAMP:20260404T111412Z UID:QChaos2020/7 DESCRIPTION:Title: Entanglement dynamics in non-unitary circuits\nby Vedika Khe mani (Stanford University) as part of Quantum Chaos 2020 Seminars\n\n\nAbs tract\nRecent work has shown that unitary circuits subject to repeated pro jective measurements can undergo an entanglement transition as a function of the measurement rate. This transition is generally understood in terms of a competition between the scrambling effects of unitary dynamics and th e disentangling effects of measurements. I will discuss how\, surprisingly \, entanglement transitions are possible even in the absence of unitary dy namics in “measurement only” models. I will talk about the entanglemen t phase diagrams in these models\, and also present results on measures of locality under non-unitary dynamics. Finally\, I will discuss a recent pr oposal to measure entanglement without issues of postselection in a class of non-unitary circuits using ideas of spacetime duality.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Bin Yan (Los Alamos National Laboratory) DTSTART:20201105T160000Z DTEND:20201105T170000Z DTSTAMP:20260404T111412Z UID:QChaos2020/8 DESCRIPTION:Title: The Quantum Zoo of Butterflies\nby Bin Yan (Los Alamos Natio nal Laboratory) as part of Quantum Chaos 2020 Seminars\n\n\nAbstract\nClas sical chaotic dynamics exhibit extreme sensitivity to initial conditions - - known as the butterfly effect. The problem in quantum mechanics\, howev er\, is much more subtle. Conventional approaches usually address quantum chaos in the energy domain\, e.g.\, spectral correlations. Recently develo pments invented different diagnostics to reveal the quantum butterfly effe ct in the time domain. The quantum butterfly effect has a much richer stru cture than its classical counterpart. In this talk\, I will tell a coheren t story and introduce various types of butterflies in the quantum world: T he famous Lorenz-Butterfly with circuit complexity\; a Bradbury-Butterfly known as a novel correlator\, the out-of-time correlator\; and an Anti-But terfly which can heal damaged information from the past.\n LOCATION:https://stable.researchseminars.org/talk/QChaos2020/8/ END:VEVENT END:VCALENDAR