Role of coherence in the nonequilibrium thermodynamics of quantum systems

Francica, Gianluca; Goold, John; Plastina, Francesco

doi:10.1103/physreve.99.042105

Cited by 133 publications

(145 citation statements)

References 92 publications

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“…Hence, to lowest order the power against friction is proportional to μ 2 . Since μ∝1/τ cycle we expect that the assymptotic power against friction scales as equation (C.2) [14].…”

Section: ( )mentioning

confidence: 99%

Quantum signatures in the quantum Carnot cycle

Dann

Kosloff

2020

New J. Phys.

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The Carnot cycle combines reversible isothermal and adiabatic strokes to obtain optimal efficiency, at the expense of a vanishing power output. Quantum Carnot-analog cycles are constructed and solved, operating irreversibly with positive power. Swift thermalization is obtained in the isotherms utilizing shortcut to equilibrium protocols and the adiabats employ frictionless unitary shortcuts. The working medium in this study is composed of a particle in a driven harmonic trap. For this system, we solve the dynamics employing a generalized canonical state. Such a description incorporates both changes in energy and coherence. This allows comparing three types of Carnot-analog cycles, Carnot-shortcut, Endo-shortcut and Endo-global. The Carnot-shortcut engine demonstrates the trade-off between power and efficiency. It posses a maximum in power, a minimum cycle-time where it becomes a dissipator and for a diverging cycle-time approaches the ideal Carnot efficiency. The irreversibility of the cycle arises from non-adiabatic driving, which generates coherence. To study the role of coherence we compare the performance of the shortcut cycles, where coherence is limited to the interior of the strokes, with the Endo-global cycle where the coherence never vanishes. The Endo-global engine exhibits a quantum signature at a short cycle-time, manifested by a positive power output while the shortcut cycles become dissipators. If energy is monitored the back action of the measurement causes dephasing and the power terminates.CA c h [4,5], which has been generalized for weak dissipation [6,7].In the quantum regime energy transfer is constrained as well by the second law of thermodynamics [8][9][10][11]. Implying that quantum heat engines are also bounded by the Carnot efficiency. Reversibility and optimal efficiency is obtained in the quantum adiabatic limit, requiring an infinite cycle-time τ cycle .

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confidence: 99%

Quantum signatures in the quantum Carnot cycle

Dann

Kosloff

2020

New J. Phys.

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“…Let ρ ref = n λ n Π n denote the spectral decomposition of some reference state used to compute the divergence, where {λ n } are the eigenvalues and {Π n } are the eigenprojectors of ρ ref . The divergence D ρ||ρ ref can be shown to be decomposed as [56,57,70,71]…”

Section: A General Descriptionmentioning

confidence: 99%

Coherence effects in the performance of the quantum Otto heat engine

2019

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The working substance fueling a quantum heat engine may contain coherence in its energy basis, depending on the dynamics of the engine cycle. In some models of quantum Otto heat engines, energy coherence has been associated with entropy production and quantum friction. We considered a quantum Otto heat engine operating at finite time. Coherence is generated and the working substance does not reach thermal equilibrium after interacting with the hot heat reservoir, leaving the working substance in a state with residual energy coherence. We observe an interference-like effect between the residual coherence (after the incomplete thermalization) and the coherence generated in the subsequent finite-time stroke. We introduce analytical expressions highlighting the role of coherence and examine how this dynamical interference effect influences the engine performance. Additionally, in this scenario in which coherence is present along the cycle, we argue that the careful tuning of the cycle parameters may exploit this interference effect and make coherence acts like a dynamical quantum lubricant. To illustrate this, we numerically consider an experimentally feasible example and compare the engine performance to the performance of a similar engine where the residual coherence is completely erased, ruling out the dynamical interference effect.

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“…[48,50,66,68]. In fact, coherence is associated quite generally with additional entropy production [69,70] and thus is not expected to offer improvements in efficiency.…”

Section: Quantum Performance Enhancements?mentioning

confidence: 99%

Quantum thermal absorption machines: refrigerators, engines and clocks

Mitchison

2019

Contemporary Physics

141

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The inexorable miniaturisation of technologies, the relentless drive to improve efficiency and the enticing prospect of boosting performance through quantum effects are all compelling reasons to investigate microscopic machines. Thermal absorption machines are a particularly interesting class of device that operate autonomously and use only heat flows to perform a useful task. In the quantum regime, this provides a natural setting in which to quantify the thermodynamic cost of various operations such as cooling, timekeeping or entanglement generation. This article presents a pedagogical introduction to the physics of quantum absorption machines, covering refrigerators, engines and clocks in detail.

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Role of coherence in the nonequilibrium thermodynamics of quantum systems

Cited by 133 publications

References 92 publications

Quantum signatures in the quantum Carnot cycle

Quantum signatures in the quantum Carnot cycle

Coherence effects in the performance of the quantum Otto heat engine

Quantum thermal absorption machines: refrigerators, engines and clocks

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