Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F57: Systems Far from Equilibrium, including Fluctuation Theorems and FluctuationDissipation RelationsFocus

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Sponsoring Units: GSNP Chair: Martin Bazant, Massachusetts Inst of TechMIT Room: BCEC 256 
Tuesday, March 5, 2019 11:15AM  11:27AM 
F57.00001: Numerical Measurement of the Anomalous Dimension in a TwoSpecies ReactionDiffusion Model Benjamin VollmayrLee, Joshua D. Hellerick, Robert C. Rhoades We consider a twospecies reactiondiffusion model that consists of the trapping reaction A+B→A with traps that either annihilate A+A→0 or coalesce A+A→A. Both species undergo diffusion with distinct diffusion constants D_{A} and D_{B}. We introduce a simulation technique that provides the full probability distribution of B particles for a given realization of the trap dynamics, greatly improving statistical accuracy. We measure in one dimension the B particle density decay exponent and the recently predicted anomalous dimension φ that appears in the asymptotic B particle correlation function C_{BB}(r,t) ∼ t^{φ }f(r/t^{1/2}). These exponents are predicted via renormalization group calculations to be universal for dimensions d≤2, depending only on the diffusion constant ratio and the trap reaction type. We compare our measured values to the renormalization group predictions, and to various exact solutions based on 3walker and 4walker problems. 
Tuesday, March 5, 2019 11:27AM  11:39AM 
F57.00002: Towards a bolometric measurement of the heat of erasure in superconducting logic Olli Saira, Matthew Matheny, Raj Katti, Gregory Wimsatt, Siyuan Han, James Crutchfield, Michael Roukes In his seminal 1961 paper, Landauer derived a lower bound on the heat dissipation by any computing device per irreversible logical operation, such as erasing (resetting) a bit. I will outline a new approach for an unencumbered measurement of the heat of bit erasure using a superconducting flux qubit and an ultrasensitive bolometer. First, using a gradiometric flux qubit as the physical bit subsystem, I will revisit a classical trajectorytracking demonstration of efficient bit erasure. Owing to the high intrinsic speed of superconducting flux logic, we are able to extract a highresolution histogram of the work exerted on the system during an erasure cycle. The experimental work histogram display universal features expected for a generic efficient implementation of bit erasure. In addition, the experimental work distributions enable us to test recentlydiscovered Fractional Fluctuation Theorems, generalizing Landauer’s erasure bound. Second, I will argue that a combination of superconducting logic cell and a bolometer is an ideal way to measure the heat of erasure through its effect on the dissipative environment. 
Tuesday, March 5, 2019 11:39AM  11:51AM 
F57.00003: Collective Power: Minimal Model for Thermodynamics of Nonequilibrium Phase Transitions Tim Herpich, Juzar Thingna, Massimiliano Esposito We propose a thermodynamically consistent minimal model to study synchronization which is made of driven and globally interacting threestate units. This system exhibits at the meanfield level two bifurcations separating three dynamical phases: a single stable fixed point, a stable limit cycle indicative of synchronization, and multiple stable fixed points. These complex emergent dynamical behaviors are understood at the level of the underlying linear Markovian dynamics in terms of metastability. Stochastic thermodynamics is used to study the dissipated work across dynamical phases as well as across scales. This dissipated work is found to be reduced by the attractive interactions between the units and to nontrivially depend on the system size. 
Tuesday, March 5, 2019 11:51AM  12:03PM 
F57.00004: Number of hidden states needed to physically implement a given conditional distribution Jeremy Owen, Artemy Kolchinsky, David Wolpert We consider the problem of constructing a physical process over a state space X that applies some desired conditional distribution P to initial states to produce final states. This problem arises in various scenarios in the thermodynamics of computation and nonequilibrium statistical physics (e.g., when designing processes to implement some desired computation, feedbackcontrol protocol, etc.). It is known that there are conditional distributions that cannot be implemented using any master equation involving just the states in X. Here we show that any conditional distribution P can be implemented if additional “hidden” states are available, and provide an upper bound on how many such states are required to implement any P in a thermodynamically reversible manner. Our results imply that for certain P that can be implemented without hidden states, having additional states available permits an implementation that generates less heat. These results can be seen as uncovering a novel type of cost of the physical resources needed to perform information processing—the size of a system’s hidden state space. 
Tuesday, March 5, 2019 12:03PM  12:15PM 
F57.00005: The thermodynamics of computing with circuits David Wolpert, Artemy Kolchinsky As Landauer showed, any physical process that implements a given computation must generate a minimal amount of heat. Common engineered systems implement computations using circuits, as do many biological systems (e.g., gene regulatory networks). The topology of such circuits introduces additional constraints on the physical system implementing the computation. One might expect that this increases the minimal amount of heat needed to implement that computation, beyond the minimal amount needed if there are no constraints on how the computation can be implemented. We derive exact equations for the minimal amount of heat that is generated by any physical process that implements a given computation using a specified circuit. We also quantify how that minimal amount of heat compares to the minimal amount when the constraint of implementing the computation with the specified circuit is removed. These results provide a rich, new set of optimization problems that must be addressed by any designer of a circuit, if they wish to minimize thermodynamic costs. 
Tuesday, March 5, 2019 12:15PM  12:27PM 
F57.00006: Population dynamics of driven autocatalytic reactive mixture Hongbo Zhao, Martin Bazant A reactive mixture undergoes thermal fluctuation and reacts with the reservoir when chemically driven. We apply the FokkerPlanck equation consistent with statistical physics to describe the ensemble dynamics. We illustrate the effect of autocatalysis on the ensemble dynamics by comparing systems with identical thermodynamics yet different reaction kinetics. Fictitious phase separation may occur in autocatalytic systems. Reversely, autoinhibition may suppress phase separation, leading to dynamic phase behavior entirely different from thermodynamic equilibrium. 
Tuesday, March 5, 2019 12:27PM  12:39PM 
F57.00007: Information Thermodynamics of Turing Patterns Gianmaria Falasco, Riccardo Rao, Massimiliano Esposito We set up a rigorous thermodynamic description of reactiondiffusion systems driven out of equilibrium by timedependent spacedistributed chemostats. Building on the assumption of local equilibrium, nonequilibrium thermodynamic potentials are constructed exploiting the symmetries of the chemical network topology. It is shown that the canonical (resp. semigrand canonical) nonequilibrium free energy works as a Lyapunov function in the relaxation to equilibrium of a closed (resp. open) system and its variation provides the minimum amount of work needed to manipulate the species concentrations. The theory is used to study analytically the Turing pattern formation in a prototypical reactiondiffusion system, the onedimensional Brusselator model, and to classify it as a genuine thermodynamic nonequilibrium phase transition. The framework paves the way to study the energy cost of pattern manipulation and information transmission in complex biochemical systems. 
Tuesday, March 5, 2019 12:39PM  12:51PM 
F57.00008: Thermolubricity and the Jarzynski equality Erio Tosatti, Franco Pellegrini, Emanuele Panizon, Giuseppe Santoro Two different pieces of physics in nanoscale sliding friction are thermolubricity and the Jarzynski identity. The first: a dry slider can at high temperature and low velocity exhibit thermolubric friction f ∝ v replacing ordinary stick–slip friction f ∝ logv in opposite conditions. The second: satisfaction (violation) of Jarzynski’s identity is tied to the abundance (scarcity) of negative work events (“free lunches”). Thermolubricity and Jarzynski are general in nature and separately met in experiments including sliding emulations in optical lattices, and protein force spectroscopy. We prove analytically and demonstrate numerically in the classical PrandtlTomlinson point slider model that the presence or absence of thermolubricity is exactly equivalent to satisfaction or violation of the Jarzynski equality. The divide between the two regimes simply coincides with the total frictional work per cycle falling below or above kT respectively. This concept can, with due caution, be extended to more complex sliders, and invites crosscheck experiments, such as searching for free lunches in cold ion sliding as well as in forced protein unwinding, and alternatively checking for a thermolubric regime in dragged colloid monolayers. 
Tuesday, March 5, 2019 12:51PM  1:03PM 
F57.00009: Dynamic critical properties of nonequilibrium Potts models with absorbing states James Stidham, Ahmadreza Azizi, Michel Pleimling We present the results of numerical simulations of nonequilibrium Potts models with absorbing states that allow for different scenarios, depending on the range of the spinspin interactions [1]. These scenarios encompass a voter critical point, as well as the presence of both a symmetrybreaking phase transition, and an absorbing phase transition. We investigate timedependent quantities that provide insights into the transient properties of the models. 
Tuesday, March 5, 2019 1:03PM  1:15PM 
F57.00010: Stability of dynamical quantum phase transitions in disordered systems Christian Mendl, Jan Carl Budich Dynamical quantum phase transitions (DQPTs) appear at critical times (socalled Fisher zeros) of the Loschmidt amplitude G(t) =〈ψe^{i H t}ψ〉, where ψ〉denotes the initial quantum state and H the Hamiltonian governing the nonequilibrium time evolution. So far DQPTs have mostly been investigated for systems with momentum conservation, but the fate of DQPTs in the presence of spatially uncorrelated disorder remains a largely open question. In this work we address this question by resorting to a supercell representation, which allows us to maintain a generalized version of the momentum space framework. Specifically, Fisher zeros appear as vortices of the complex phase of G(t) in the momentumtime plane; these vortices can only continuously change with the onset of disorder. Thus we hope to shed light on the dynamical behavior of disordered systems out of equilibrium. 
Tuesday, March 5, 2019 1:15PM  1:27PM 
F57.00011: Femtosecond imaging of nonequilibrium phase transitions: Symmetry breaking and prethermalization in interacting CDW systems Joseph Williams, Faran Zhou, Tianyin Sun, Mercouri Kanatzidis, Christos Malliakas, Chongyu Ruan In correlated manybody systems, the fundamental processes of spontaneous symmetry breaking (SSB) to form longrange order may be intercepted by competing interactions between particles. In such cases, the transition becomes sharp over the control parameters, and surprising synchronicity develops to manifest macroscopic switching between two stable longrange orders. This departure from SSB behavior has been the hallmark of macroscopic switching of quantum materials, but never before have the microscopic processes been captured with atomic detail. Here we demonstrate a surprising postlaserquench selforganization of an interacting CDW system exhibiting critical slowdown near thermal and interaction driven critical points. Unlike in SSB system, such photoinduced criticalities primarily emerged in the time domain and manifested in the prethermalization and dynamical phase transition. Using femtosecond (fs) imaging, we capture these highly tunable, nonequilibrium processes and the emerging unconventional symmetrybroken intermediate state, opening up an entirely new dimension in studying and controlling phase transitions far from equilibrium. 
Tuesday, March 5, 2019 1:27PM  1:39PM 
F57.00012: Nanoscale virtual potentials using optical tweezers John Bechhoefer, Avinash Kumar We combine optical tweezers with feedback to impose arbitrary timedependent potentials on a colloidal particle. The feedback trap detects a particle's position, calculates a force based on an imposed “virtual potential,” and shifts the trap center to generate the desired force. This kind of feedback trap can both extend the capabilities of optical tweezers and test fundamental ideas in stochastic thermodynamics. For the former, we have controlled trap stiffness to make tweezer response truly isotropic in three dimensions, allowing unbiased measurement of dynamics. For the latter, we have created virtual doublewell potentials with well separations of 11 nm and dwell times of a few ms, scales that approach those of proteinfolding dynamics. Such a speedup of dynamics will allow measurement of stochastic trajectorybased quantities for systems far from equilibrium. 

F57.00013: ABSTRACT WITHDRAWN

Tuesday, March 5, 2019 1:51PM  2:03PM 
F57.00014: Generalization of the Boltzmann distribution to systems out of equilibrium Milo Lin

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