Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session LL05: V: Thermodynamics in Quantum Information and Phase Transitions |
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Sponsoring Units: GSNP DQI DCMP Chair: Giacomo Guarnieri, Freie Universität Berlin Room: Virtual Room 5 |
Tuesday, March 21, 2023 5:00AM - 5:12AM |
LL05.00001: Thermodynamics of quantum switch information capacity activation Xiangjing Liu, Oscar Dahlsten, Daniel Ebler We address a new setting where the second law is under question: thermalizations in a quantum superposition of causal orders, enacted by the so-called quantum switch. This superposition has been shown to be associated with an increase in the communication capacity of the channels, yielding an apparent violation of the data-processing inequality and a possibility to separate hot from cold. We analyze the thermodynamics of this information capacity increasing process. We show how the information capacity increase is compatible with thermodynamics. We show that there may indeed be an information capacity increase for consecutive thermalizations obeying the first and second laws of thermodynamics if these are placed in an indefinite order and moreover that only a significantly bounded increase is possible. The increase comes at the cost of consuming a thermodynamic resource, the free energy of coherence associated with the switch. |
Tuesday, March 21, 2023 5:12AM - 5:24AM |
LL05.00002: Thermodynamics of precision in quantum non-equilibrium steady-states GIACOMO GUARNIERI Autonomous engines operating at the nanoscale can be prone to deleterious fluctuations in the heat and particle currents. Thermodynamic uncertainty relations (TURs) express a fundamental lower bound which translates a trade-off relation between precision and entropy production. Importantly, recent studies have shown that they can be violated in the quantum regime, thus motivating the search for analogous quantum counterparts. In this paper, we show that the geometry of quantum nonequilibrium steady states alone directly implies the existence of TUR, but with a looser bound, which is not violated by the above recent findings. The geometrical nature of this result makes it extremely general, establishing a fundamental limit for the thermodynamics of precision. Our proof is based on the McLennan-Zubarev ensemble, which provides an exact description of nonequilibrium steady states. We first prove that the entropy production of this ensemble can be expressed as a quantum relative entropy. The TURs are then shown to be a direct consequence of the Cramer-Rao bound, a fundamental result from parameter estimation theory. By combining techniques from many-body physics and information sciences, our approach also helps to shed light on the delicate relationship between quantum effects and current fluctuations in autonomous machines, where new general bound on the power output are found and discussed. |
Tuesday, March 21, 2023 5:24AM - 5:36AM |
LL05.00003: Quantum energetics of non-commuting measurements in a circuit quantum electrodynamics system Xiayu Linpeng, Maria Maffei, Nicolò Piccione, Samyak Prasad, Léa Bresque, Andrew N Jordan, Alexia Auffèves, Kater Murch When the measurement observable does not commute with the system Hamiltonian, the energy of the measured system is typically not conserved during the measurement. Instead, energy is transferred between the measured system and the measuring meter. In this work, we have studied this effect in a circuit quantum electrodynamics system containing a transmon qubit embedded in a 3D microwave cavity. The qubit is dispersively coupled to the cavity, which enables quantum non-demolition (energy-conserving) measurement of the qubit states. By applying an additional microwave drive on resonance with the qubit frequency, the Hamiltonian of the qubit is modified, leading to a non-commuting measurement that is not energy-conserving. We investigate the energy exchange between the qubit and the cavity by performing a spectral analysis of the cavity field during the measurement. In the spectra, due to the microwave drive, the Mollow triplets can be clearly observed. The two side peaks show different intensities, indicating an effective frequency shift that compensates for the energy change of the qubit during the measurement. While the energy is not conserved for the qubit, the total energy of the qubit and the cavity field is still a conserved quantity. This energy transfer occurs without the need to know the measurement outcome, which could potentially be utilized for autonomous quantum engines. |
Tuesday, March 21, 2023 5:36AM - 5:48AM |
LL05.00004: Using a single thermometer to estimate two temperatures Harshit Verma We consider the question: Is it possible to measure two temperatures simultaneously using a single quantum thermometer? In a scenario involving local thermometry, we affirm that this task can indeed be accomplished with the assistance of quantum control. In particular, we consider a composite particle with at least two quantum degrees of freedom (DoF) as a thermometer, where one DoF is susceptible to the local temperature whereas the other DoF is quantum-controlled. For thermalization to two temperatures, the thermometer is exposed to two baths at distinct temperatures with a quantum controlled interaction, or a purified single bath whose state is quantum controlled in addition to the interaction. We show that such a particle, if used in a Mach-Zehnder interferometer or a quantum switch with such engineered bath(s)/interactions, can be used to estimate two temperatures simultaneously. For all of the setups -- that allow simultaneous two temperature thermometry -- which we consider, we obtain the variance in the estimated temperatures through the multi-parameter Cram'er-Rao bound. Our results establish the utility of quantum control in a novel metrological task besides opening new avenues for further applications, such as quantum thermodynamics with two thermal baths along with quantum control. |
Tuesday, March 21, 2023 5:48AM - 6:00AM |
LL05.00005: Critical and multicritical points in the three-dimensional Z2 gauge theory with matter -- an information bottleneck perspective Zohar Ringel, Lior Oppenheim, Snir Gazit, Maciej Koch-Janusz Lattice gauge theories are a subject of great importance to many domains of physics, from particle physics to quantum computing. Despite extensive research, many open problems still exist. In particular, the recent interest in self-dual gauge theories has brought to the forefront the old question of RG treatment of such systems, or, more concretely put, how to locally coarse-grain discrete gauge fields. Here we apply the recently proposed Real Space Mutual Information (RSMI) approach to the 3D Ising gauge theory with matter. This technique, employing neural-network-based estimation and information bottlenecks, allows us to peer into the structure of the critical and multi-critical points in the theory. It provides direct access to leading and sub-leading operators, along with their symmetries and degeneracies. While this type of data is accessible for 2D critical systems via direct diagonalization techniques, for 3D critical systems we are not aware of a competing method capable of extracting such information in practice. We will briefly discuss the bearing of our numerical findings on the conjecture that the multi-critical point in this 3D system is an emergent XY theory. |
Tuesday, March 21, 2023 6:00AM - 6:12AM |
LL05.00006: Low-power-consumption quantum analog Ising machine based on overdamped bistability with stochastic resonance effect Zhiqiang Liao, Hiroyasu Yamahara, Hitoshi Tabata Gain-dissipative Ising machine (GIMs) are dedicated devices that utilizing the interplay of linear gain dynamics with a symmetric bistability to rapidly solve combinatorial optimization problems. However, to prevent the spin state from being switched randomly by thermal noise, the saturated fixed-point amplitude of traditional GIMs should be significantly larger than the environmental noise intensity, which results in a relatively high-power consumption. To break through the existing limitation on power consumption, this work proposes an overdamped bistable stochastic resonance unit (OBSRU) as the nonlinearity for constructing the GIM. The numerical simulation shows that OBSRU can correctly simulate the symmetric bistability of isolated spins. In addition, domain clustering dynamics benchmark shows that the stochastic resonance characteristics of the OBSRU enable GIM to effectively suppress noise-induced random spin state switching; therefore, it can work normally with small amplitude in the environment with relatively high noise level. Some prevalent MAXCUT problems, such as Moebius ladder and G-set graphs, are also used as benchmarks to evaluate the performance of OBSRU-based GIM in a noisy environment. The results show that compared with the traditional GIM, the OBSRU-based GIM can achieve the comparable accuracy with significantly lower power consumption. The results reveal that the proposed OBSRU-based GIM provides a promising architecture for low-power-consumption GIM. |
Tuesday, March 21, 2023 6:12AM - 6:24AM |
LL05.00007: Finite-Time Dynamical Phase Transition in Nonequilibrium Relaxation Jan N Meibohm, Massimiliano Esposito We uncover a finite-time dynamical phase transition in the thermal relaxation of a mean-field magnetic model. The phase transition manifests itself as a cusp singularity in the probability distribution of the magnetization that forms at a critical time. The transition is due to a sudden switch in the dynamics, characterized by a dynamical order parameter. We derive a dynamical Landau theory for the transition that applies to a range of systems with scalar, parity-invariant order parameters. Close to criticality, our theory reveals an exact mapping between the dynamical and equilibrium phase transitions of the magnetic model, and implies critical exponents of mean-field type. We argue that interactions between nearby saddle points, neglected at the mean-field level, may lead to critical, spatiotemporal fluctuations of the order parameter, and thus give rise to novel, dynamical critical phenomena.
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Tuesday, March 21, 2023 6:24AM - 6:36AM |
LL05.00008: Hidden Mattis Order and Dynamic Correlations in the Annealed Ising Spin Glass Ding Wang, Lei-Han Tang The hidden Mattis phase of annealed spin-glass models was suggested by Kasai and Okiji 40 years ago but received relatively little attention until very recently. In terms of equilibrium configurations, the phase is characterized by a spin-glass type order but no thermodynamic signature across the transition. To better understand the static and dynamic correlations implied by the hidden order, we performed detailed numerical simulations of the Sherrington-Kirkpatrick (SK) Ising spin glass model with annealed coupling constants. Relaxation from the initial spin glass state towards the stationary state is studied when the interactions are allowed to evolve with time under the usual Metropolis updating scheme. The spectrum of the instantaneous interaction matrix is monitored during the simulation and our results generally agree with the analytical predictions . Above the transition, the spectrum remains essentially the same as that of the initial random matrix, but a gap appears in the low temperature Mattis phase that separates the largest eigenvalue from the rest of the spectrum. The autocorrelation of spins and of the eigenvector with the largest eigenvalue in the stationary state are studied. Our data show that the finite-size scaling exponent of the autocorrelation functions changes as temperature changes. At low temperatures the spin configuration and the eigenvector are closely correlated, and this correlation disappears above the transition. Hence the hidden Mattis order can be associated with the formation of a system-wide condensate of spins that drifts in configuration space. More complex dynamical behavior in the neighborhood of the transition will also be reported. |
Tuesday, March 21, 2023 6:36AM - 6:48AM |
LL05.00009: Unexpected upper critical dimension for spin glass models in a field predicted by the loop expansion around the Bethe solution at zero temperature Gianmarco Perrupato, Maria Chiara Angelini, Giorgio Parisi, Federico Ricci-Tersenghi, Carlo Lucibello, Tommaso Rizzo The spin-glass transition in a field in finite dimension is analyzed directly at zero temperature using a perturbative loop expansion around the Bethe lattice solution. The loop expansion is generated by the M-layer construction whose first diagrams are evaluated numerically and analytically. The generalized Ginzburg criterion reveals that the upper critical dimension below which mean-field theory fails is DU=8, at variance with the classical result DU=6 yielded by finite-temperature replica field theory. Our expansion around the Bethe lattice has two crucial differences with respect to the classical one. The finite connectivity z of the lattice is directly included from the beginning in the Bethe lattice, while in the classical computation the finite connectivity is obtained through an expansion in 1/z. Moreover, if one is interested in the zero temperature (T=0) transition, one can directly expand around the T=0 Bethe transition. The expansion directly at T=0 is not possible in the classical framework because the fully connected spin glass does not have a transition at T=0, being in the broken phase for any value of the external field. |
Tuesday, March 21, 2023 6:48AM - 7:00AM |
LL05.00010: On the structure of the active Fokker-Planck equation pedro herrera avila, Mario Sandoval Recently, it has been experimentally discovered, and theoretically proved, that the stationary velocity distribution function of a non-interactive active stochastic system is bimodal. In this work, we theoretically reveal the condition under which a bimodal distribution will arise, and the condition under which this bimodal distribution will become Gaussian. This condition depends on two important time scales in the problem, namely, reorientation and inertial time scales. Briefly, when the inertial time is larger than the orientation time, the active Fokker-Planck stationary solution admits a bimodal structure. The inverse condition is seen to admit a Gaussian structure. |
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