Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 510)
Virtual (March 2022); Time Zone: Pacific Time
Session S66: Open Quantum Systems IIFocus

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Sponsoring Units: DAMOP Chair: Guoqing Wang, Massachusetts Institute of Technology MI Room: Room 413 
Thursday, March 9, 2023 8:00AM  8:36AM 
S66.00001: Constructing open manybody quantum systems with atoms, cavities and light Invited Speaker: Dan M StamperKurn Trapping ultracold atoms within strongly coupled optical cavities allow us to engineer rich manybody quantum systems that are essentially open. I will describe experiments in which single, few, or many ultracold atoms are placed with high spatial control within FabryPerot optical cavities. Our focus generally is on pushing the limits of quantum measurement, and also exerting feedback control over quantum properties of the atomic system. I will discuss three main results: highfidelity midcircuit measurement within an atomic tweezer array, precise detection of an atomic ensemble undergoing nonequilibrium thermodynamics, and autonomous feedback stabilization of an atomic spin system. 
Thursday, March 9, 2023 8:36AM  8:48AM 
S66.00002: Lattice relaxation times for spin qubits in MOFs with semiempirical spectral densities Katy Aruachan Fajardo, Yamil J Colón, Daniel D Aravena Ponce, Felipe F Herrera Understanding the mechanisms that determine relaxation times for molecular spin qubits in metalorganic framework (MOF) crystals is essential for applications in precision measurements and quantum information processing [1]. Recent spinecho experiments on the spin relaxation of vanadylbased qubits as a function of magnetic field and temperature has stimulated the development of phenomenological and abinitio quantum mechanical modeling techniques [13]. We propose an alternative method with a semiempirical approach for building Redfield quantum master equations based on a stochastic fluctuation model for the molecular gyromagnetic tensor due to the interaction of molecular spin impurities with crystal lattice vibrations. The spin relaxation rates are obtained from a semiempirical bath autocorrelation function that captures the experimental temperature dependence through a fitting procedure. These model spectral densities are used for computing the spin population and decoherence dynamics of vanadylbased spin qubits beyond cryogenic temperatures (>50 K) and high magnetic fields, where the Zeeman effect dominate the relaxation dynamics. Our results quantitatively agree with experiments [3] and represent a solid foundation for the theoretical characterization of other spin qubits in MOFs, for the rational design of novel quantum magnetometers based on this material class. 
Thursday, March 9, 2023 8:48AM  9:00AM 
S66.00003: Lamb shift for the detection of the Unruh effect Navdeep Arya, D. Jaffino Stargen, Kinjalk Lochan, Sandeep K Goyal The Unruh effect states that a uniformly accelerated observer perceives the inertial vacuum as a thermal state at a temperature proportional to the observer's acceleration. At the accelerations achievable in laboratory settings, the thermal signature in the atom’s response is so feeble that the Unruh effect has eluded experimental detection till now. Numerous physical observables, including atomic transition rates, particle decay rates, and geometric phase, have been studied under varied settings as possible candidates for capturing a measurable and unambiguous signature of the Unruh effect. 
Thursday, March 9, 2023 9:00AM  9:12AM Author not Attending 
S66.00004: Dissipative dynamics of an impurity with spinorbit coupling Alberto Cappellaro Spinorbit coupling (SOC) plays a central role in topological phases of matter. In reality, all of these topological materials are coupled to some dissipative environment, which affects the robustness of the phase. Surprisingly, SOC and dissipation are rarely considered together, which hinders our understanding of the interplay between the two phenomena. Here, we fill this gap by considering dissipative dynamics of a spinorbit coupled particle in one dimension. 
Thursday, March 9, 2023 9:12AM  9:24AM 
S66.00005: First order phase transition in a dissipative BoseHubbard chain Robbe Ceulemans Atomic condensates are attractive simulators to study quantum systems at equilibrium thanks to their highly controllable nature. In recent years, they have also become more prominent in studies on nonequilibrium physics. One way to achieve outofequilibrium ultracold gases is by introducing dissipation, which can be done in a controllable way. In this talk we theoretically address a BoseHubbard chain with losses at one site in the centre, using the Truncated Wigner approximation. We observe bimodality and critical behaviour in the nonequilibrium steady states of the dissipative site, qualitatively corresponding to experimental observations. This indicates the presence of a first order phase transition. Further, we investigate the ability of a more compact, effective description to reproduce this steadystate physics. We find that the suggested model approaches the steady states remarkably well with small deviations in its dynamical properties like the effective Liouvillian gap. The dark soliton state, observed in simulations of the dissipative BoseHubbard model, can also be reproduced with this effective description. 
Thursday, March 9, 2023 9:24AM  9:36AM 
S66.00006: Limitations of a multiRamanpulse atom interferometry acceleration sensor Philip C Chrostoski, Scott Bisson, Daniel B Soh Given that atom interferometry has been the most successful quantum sensing application, ways to increase the sensitivity is a current topic of interest. One way to increase the sensitivity is an increase in the momentum axis by providing a larger momentum to the atom cloud. This has been done through increasing the number of central Raman π − pulses. In this approach, a longer stay in the intermediate high energy state, which is often neglected through adiabatic elimination due to large optical detuning, causes a higher chance of undesired spontaneous decay. The loss of quantum information of the atomic states due to this undesired spontaneous decay will add an additional error to the atom interferometer. In this work, we consider an open quantum system using the Lindblad master equation to devise a model for the atomic state dynamics that incorporates the undesired spontaneous decay. We formulate a noise model and combined it with the meanvaluedeviation to analyze our figure of merit error in the measurement of local acceleration. Our theoretical results show the measurement error will be dominated by the inverse square noise dependence on the number of Raman pulses in low numbers of Raman pulses, while that in the high numbers of Raman pulses will be dominated by the loss of quantum information through the undesired spontaneous decay in the intermediate high energy state. 
Thursday, March 9, 2023 9:36AM  9:48AM 
S66.00007: Why the dissipative gap fails to predict relaxation times in dissipative lattice models Gideon Lee, Alexander McDonald, Aashish A Clerk Quantum systems exhibiting effective nonHermitian dynamics are the subject of considerable recent interest. Among their most striking features is the nonHermitian skin effect (NHSE), where a small change in boundary conditions can completely change the spectrum and localization of eigenmodes. Recent work suggests that the NHSE directly also yields surprising dynamics: anomalously long relaxation times that are not simply given by the dissipative gap of the system's Liouvillian, but instead grow with system size and depend on the NHSE localization length ξ_{loc}. Despite the simplicity of the underlying argument, we show here that the situation is often more complex: a subtle interference effect makes the extreme localization of modes largely irrelevant in determining relaxation times. Focusing on a fully quantum opensystems implementation of the paradigmatic HatanoNelson model [1], we show why this intuitive interference effect must occur, how it helps determine anomalous relaxation times, and how this physics is ultimately a consequence of locality. We also show that there is a crucial sensitivity to particle statistics (i.e. fermionic versus bosonic models), and that similar effects occur in other nonHermitian quantum lattice models. 
Thursday, March 9, 2023 9:48AM  10:00AM 
S66.00008: First Devices with Transport Properties Outside the Onsager Relation Jochen D Mannhart According to Onsager’s reciprocal relation [1], in linear response, the probability of electron transfer through any twoterminal device must be symmetric with respect to the reversal of the current direction. All known devices obey this symmetry. 
Thursday, March 9, 2023 10:00AM  10:12AM 
S66.00009: Matching perturbative and nonperturbative descriptions of the reorganization energy Evgeny Mozgunov, Yangheng Jizhe We revisit an old concept of reorganization energy that appears in Marcus theory and, more recently, in the flux qubit tunneling experiments. Reorganization energy can be observed in the initialstatedependent shift of the tunneling rate peak from the zerobias point of the flux qubit. Taking advantage of the various open system methods developed for quantitative prediction of the general evolution of flux qubits in quantum annealing, we investigate the specific setting of the tunneling experiment. We find that both perturbative and nonperturbative methods demonstrate a shift in the tunneling rate peak. Rigorous ranges of validity of those methods allow us to observe with controlled numerical precision the crossover between the Lorenzian and the Gaussian shapes of the peak, as well as the adjustments on the value of the shift. The ranges of validity overlap only for a special case of the bath, but the qualitative insights we draw are applicable for the realistic bath as well. 
Thursday, March 9, 2023 10:12AM  10:24AM Author not Attending 
S66.00010: Pseudomode description of general open quantum systems with applications to thermodynamics Graeme Pleasance, Francesco Petruccione The pseudomode method has been recognized as a powerful tool for the description of nonMarkovian open system dynamics. The technique is based on replacing a bosonic environment with a small set of damped harmonic oscillators  the pseudomodes  thereby mapping the initial system onto a simpler configuration described by a Markovian master equation. In this talk, we present an efficient mapping scheme that combines several key features of previous approaches, enabling the optimal construction of pseudomode networks representing general nonMarkovian environments. For special cases involving nonHermitian systempseudomode interactions, we also establish general conditions under which the corresponding master equation may be converted into GoriniKossakowskiSudarshanLindblad (GKSL) form. Finally, we demonstrate the application of our results by analyzing the performance of a quantum Otto cycle at strong systembath coupling. 
Thursday, March 9, 2023 10:24AM  10:36AM 
S66.00011: Controlling bright and dark periods of entanglement in dissipative interacting qubits using a radiation field Gehad K Sadiek, Rahma Abdelmagid Quantum logic gates demand a coherent controllable coupling among qubits. One of the main obstacles toward realizing a practical quantum computer is decoherence in the qubits due to their inevitable interaction with the environment. It was shown that entanglement between two noninteracting, but initially entangled, qubits may suffer sudden death, with no revival, due to coupling to pure vacuum noise (Yu and Eberly 2004 Phys. Rev. Lett. 93 140404 ). Furthermore, two interacting qubits coupled to a dissipative or dephasing environment were found to exhibit bright and dark periods of entanglement dynamics. In this work, we show how the exposure of such a dissipative coupled qubits system to a quantum radiation field would significantly affect the durations of these periods and may entirely eliminate them depending on the initial state of the system and its enclosed entanglement as well as the radiation intensity. The thermal effect of the environment on the system dynamics is explored as well. 
Thursday, March 9, 2023 10:36AM  10:48AM 
S66.00012: Topological synchronization of quantum van der Pol oscillators Christopher W Wächtler, Gloria Platero To observe synchronization in large networks of classical or quantum systems demands both excellent control of the interactions between nodes and very accurate preparation of initial conditions due to the involved nonlinearities and dissipation. This limits its applicability for future devices. We demonstrate a route towards significantly enhancing the robustness of synchronized behavior in open nonlinear systems that utilizes the power of topology. In lattices of quantum van der Pol oscillators with topologically motivated couplings, boundary synchronization emerges in the classical mean field as well as the quantum regime. In addition to its robustness against disorder and initial state perturbations, the observed dynamics is independent of the underlying topological model provided the existence of topological zeroenergy modes. Our work extends the notion of topology to the general nonlinear dynamics and open quantum system realm with applications to networks where specific nodes need special protection like power grids or quantum networks. 
Thursday, March 9, 2023 10:48AM  11:00AM 
S66.00013: Liouvillian gap and single spinflip dynamics in the dissipative FermiHubbard model Hironobu Yoshida, Hosho Katsura Motivated by recent progress in coldatom experiments, we analyze the SU(N) FermiHubbard model on a ddimensional hypercubic lattice with twobody loss. By focusing on states near the ferromagnetic steady states, we obtain the Liouvillian gap in closed form for any d and N. We also investigate the dynamics of a ferromagnetic initial state with a single spin flip analytically in strongly and weaklyinteracting and dissipative limits and numerically for various values of the parameters. Then we show that, by decreasing the strength of the interaction and loss, a crossover from the powerlaw decay to the exponential decay occurs. We expect that our findings can be tested experimentally with ultracold alkalineearthlike atoms in an optical lattice. 
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