Kinetics and thermodynamics of a driven open quantum system

in Physical Review. E ,Statistical, Nonlinear, and Soft Matter Physics (2017), 96(5),

Carnot efficiency at divergent power output

in Europhysics Letters (2017), 118(40003),

The widely debated feasibility of thermodynamic machines achieving Carnot efficiency at finite power has been convincingly dismissed. Yet, the common wisdom that efficiency can only be optimal in the ... [more ▼]

The widely debated feasibility of thermodynamic machines achieving Carnot efficiency at finite power has been convincingly dismissed. Yet, the common wisdom that efficiency can only be optimal in the limit of infinitely slow processes overlooks the dual scenario of infinitely fast processes. We corroborate that efficient engines at divergent power output are not theoretically impossible, framing our claims within the theory of Stochastic Thermodynamics. We inspect the case of an electronic quantum dot coupled to three particle reservoirs to illustrate the physical rationale. [less ▲]

Quantum and Information Thermodynamics: A Unifying Framework Based on Repeated Interactions

in Physical Review X (2017), 7(021003),

We expand the standard thermodynamic framework of a system coupled to a thermal reservoir by <br />considering a stream of independently prepared units repeatedly put into contact with the system. These ... [more ▼]

We expand the standard thermodynamic framework of a system coupled to a thermal reservoir by <br />considering a stream of independently prepared units repeatedly put into contact with the system. These <br />units can be in any nonequilibrium state and interact with the system with an arbitrary strength and <br />duration. We show that this stream constitutes an effective resource of nonequilibrium free energy, and we <br />identify the conditions under which it behaves as a heat, work, or information reservoir. We also show that <br />this setup provides a natural framework to analyze information erasure (“Landauer’s principle”) and <br />feedback-controlled systems (“Maxwell’s demon”). In the limit of a short system-unit interaction time, we <br />further demonstrate that this setup can be used to provide a thermodynamically sound interpretation to <br />many effective master equations. We discuss how nonautonomously driven systems, micromasers, lasing <br />without inversion and the electronic Maxwell demon can be thermodynamically analyzed within our <br />framework. While the present framework accounts for quantum features (e.g., squeezing, entanglement, <br />coherence), we also show that quantum resources do not offer any advantage compared to classical ones in <br />terms of the maximum extractable work. [less ▲]

Kinetics and thermodynamics of a driven open quantum system

in Physical Review. E. (2017), 96(5),

Overdamped stochastic thermodynamics with multiple reservoirs

in Physical Review. E ,Statistical, Nonlinear, and Soft Matter Physics (2016), 94(062148),

After establishing stochastic thermodynamics for underdamped Langevin systems in contact with multiple reservoirs, we derive its overdamped limit using timescale separation techniques. The overdamped ... [more ▼]

After establishing stochastic thermodynamics for underdamped Langevin systems in contact with multiple reservoirs, we derive its overdamped limit using timescale separation techniques. The overdamped theory is different from the naive theory that one obtains when starting from overdamped Langevin or Fokker-Planck dynamics and only coincides with it in the presence of a single reservoir. The reason is that the coarse-grained fast momentum dynamics reaches a nonequilibrium state, which conducts heat in the presence of multiple reservoirs. The underdamped and overdamped theory are both shown to satisfy fundamental fluctuation theorems. Their predictions for the heat statistics are derived analytically for a Brownian particle on a ring in contact with two reservoirs and subjected to a nonconservative force and are shown to coincide in the long-time limit. [less ▲]

Conservation laws and symmetries in stochastic thermodynamics

in Physical Review. E ,Statistical, Nonlinear, and Soft Matter Physics (2016), 94(052117),

Phenomenological nonequilibrium thermodynamics describes how fluxes of conserved quantities, such as matter, energy, and charge, flow from outer reservoirs across a system and how they irreversibly ... [more ▼]

Phenomenological nonequilibrium thermodynamics describes how fluxes of conserved quantities, such as matter, energy, and charge, flow from outer reservoirs across a system and how they irreversibly degrade from one form to another. Stochastic thermodynamics is formulated in terms of probability fluxes circulating in the system’s configuration space. The consistency of the two frameworks is granted by the condition of local detailed balance, which specifies the amount of physical quantities exchanged with the reservoirs during single transitions between configurations. We demonstrate that the topology of the configuration space crucially determines the number of independent thermodynamic affinities (forces) that the reservoirs generate across the system and provides a general algorithm that produces the fundamental affinities and their conjugate currents contributing to the total dissipation, based on the interplay between macroscopic conservations laws for the currents and microscopic symmetries of the affinities. [less ▲]

Fluctuation-Dissipation Relations Far from Equilibrium

in Physical Review Letters (2016), 117(180601),

Near equilibrium, where all currents of a system vanish on average, the fluctuation-dissipation relation (FDR) connects a current’s spontaneous fluctuations with its response to perturbations of the ... [more ▼]

Near equilibrium, where all currents of a system vanish on average, the fluctuation-dissipation relation (FDR) connects a current’s spontaneous fluctuations with its response to perturbations of the conjugate thermodynamic force. Out of equilibrium, fluctuation-response relations generally involve additional nondissipative contributions. Here, in the framework of stochastic thermodynamics, we show that an equilibriumlike FDR holds for internally equilibrated currents, if the perturbing conjugate force only affects the microscopic transitions that contribute to the current. We discuss the physical requirements for the validity of our result and apply it to nanosized electronic devices. [less ▲]

Dissipation in small systems: Landau-Zener approach

in Physical Review. E ,Statistical, Nonlinear, and Soft Matter Physics (2016), 93(062118),

We establish a stochastic thermodynamics for a Fermionic level driven by a time-dependent force and interacting with initially thermalized levels playing the role of a reservoir. The driving induces ... [more ▼]

We establish a stochastic thermodynamics for a Fermionic level driven by a time-dependent force and interacting with initially thermalized levels playing the role of a reservoir. The driving induces consecutive avoided crossings between system and reservoir levels described within Landau-Zener theory. We derive the resulting system dynamics and thermodynamics and identify energy, work, heat, entropy, and dissipation. Our theory perfectly reproduces the numerically exact quantum work statistics obtained using a two point measurements approach of the total energy and provides an explicit expression for the dissipation in terms of diabatic transitions. [less ▲]

Quantum Thermodynamics with Degenerate Eigenstate Coherences

in Entropy (2016), 18(447),

We establish quantum thermodynamics for open quantum systems weakly coupled to their reservoirs when the system exhibits degeneracies. The first and second law of thermodynamics are derived, as well as a ... [more ▼]

We establish quantum thermodynamics for open quantum systems weakly coupled to their reservoirs when the system exhibits degeneracies. The first and second law of thermodynamics are derived, as well as a finite-time fluctuation theorem for mechanical work and energy and matter currents. Using a double quantum dot junction model, local eigenbasis coherences are shown to play a crucial role on thermodynamics and on the electron counting statistics. [less ▲]

Stochastic thermodynamics of rapidly driven quantum systems,

in New Journal of Physics (2015), 17

We present the stochastic thermodynamics analysis of an open quantum system weakly coupled to multiple reservoirs and driven by a rapidly oscillating external field. The analysis is built on a modified ... [more ▼]

We present the stochastic thermodynamics analysis of an open quantum system weakly coupled to multiple reservoirs and driven by a rapidly oscillating external field. The analysis is built on a modified stochastic master equation in the Floquet basis. Transition rates are shown to satisfy the local detailed balance involving the entropy flowing out of the reservoirs. The first and second law of thermodynamics are also identified at the trajectory level. Mechanical work is identified by means of initial and final projections on energy eigenstates of the system. We explicitly show that this two step measurement becomes unnecessary in the long time limit. A steady-state fluctuation theorem for the currents and rate of mechanical work is also established. This relation does not require the introduction of a time reversed external driving which is usually needed when considering systems subjected to time asymmetric external fields. This is understood as a consequence of the secular approximation applied in consistency with the large time scale separation between the fast driving oscillations and the slower relaxation dynamics induced by the environment. Our results are finally illustrated on a model describing a thermodynamic engine. [less ▲]