Collective performance of a finite-time quantum Otto cycle

Kloc, Michal; Cejnar, Pavel; Schaller, Gernot

doi:10.1103/physreve.100.042126

Cited by 54 publications

(44 citation statements)

References 78 publications

(129 reference statements)

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“…Some designs of thermal machines using many-body working medium have already been studied in [87,93] where it was reported that collective effects can be beneficial when using non-adiabatic strokes instead of the usual adiabatic ones. Power increase was also pointed out for ensembles of spins 1/2 in [94] where the equilibration speed-up stemming from collective effects allows one to reduce the duration of the cycle, and hence increase the delivered power. Other studies investigate the effect of internal coupling and entanglement between the subsystems constituting the many-body working medium (pair of twolevel systems [7,84], pair of degenerate two-level systems [11], a two-level system coupled to a harmonic oscillator [85,95], and ensemble of spins 1/2 [86]).…”

Section: A Effective Amplificationmentioning

confidence: 85%

“…Note that we did not take into account the equilibration speed-up emerging form collective effects [94]. This implies that our rough estimate of the equilibration timescale (g 2 τ c ) −1 is probably overestimating the actual equilibration time.…”

Section: Appendix G: Effective Amplificationmentioning

confidence: 97%

“…In particular, still for β h > 0, there is a threshold for the value of ns beyond which indistinguishability leads only to smaller work extractions, showing again that indistinguishability-induced enhancements are not systematic and require a detailed analysis. One should note that we did not mention and study equilibration speed-up emerging from collective effects [94]. Taking into consideration the reduction of time period of each cycle one can obtain higher power increases.…”

Section: A Effective Amplificationmentioning

confidence: 97%

See 2 more Smart Citations

Thermodynamics from indistinguishability: Mitigating and amplifying the effects of the bath

Latune

Sinayskiy

Petruccione

2019

Phys. Rev. Research

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Rich quantum effects emerge when several quantum systems are indistinguishable from the point of view of the bath they interact with. In particular, delocalised excitations corresponding to coherent superposition of excited states (reminiscent of double slit experiments or beam splitters in interferometers) appear and change drastically the dynamics and steady state of the systems. Such phenomena, which are central mechanisms of superradiance, present interesting properties for thermodynamics and potentially other quantum technologies. Indeed, a recent paper [C.L. Latune, I. Sinayskiy, F. Petruccione, Phys. Rev. A 99, 052105 (2019)] studies these properties in a pair of indistinguishable two-level systems and points out surprising effects of mitigation and amplification of the bath's action on the energy and entropy of the pair. Here, we generalise the study to ensembles of arbitrary number of spins of arbitrary size. We confirm that the previously uncovered mitigation and amplification effects remain, but also that they become more and more pronounced with growing number of spin and growing spin size. Moreover, we also investigate the free energy and the entropy production of the overall dissipation process and find dramatic reductions of irreversibility. The possibility of mitigating or amplifying the effects of the baths is highly desirable in quantum thermodynamics if one wants to optimise the use of the baths to enhance the performance of thermodynamic tasks. As illustrative application of these effects, we show explicitly the large power enhancements that can be obtained in cyclic thermal machines. The reduction of irreversibility is also a promising aspect since irreversibility is known to limit the performance of thermal machines. Beyond thermodynamics, the above findings might lead to interesting applications in state protection, quantum computational tasks, light harvesting devices, quantum biology, but also for the study of entropy production. Moreover, an experimental observation [J. M. Raimond, P. Goy, M. Gross, C. Fabre, and S. Haroche, Phys. Rev. Lett. 49, 117 (1982)] confirms that such effects are indeed within reach.observables J z and J 2 := J 2 x + J 2 y + J 2 z . Such eigenvectors are denoted by |J, m in reference to their associated eigenvalues,with −J ≤ m ≤ J and J ∈ [J 0 ; ns], where J 0 = 0 if s ≥ 1 and J 0 = 1/2 if s = 1/2 and n odd. A quick calculation shows that the natural basis contains (2s + 1) n elements whereas there are only (ns + 1) 2 (or (ns + 1/2)(ns + 3/2) when s = 1/2 and n is odd) different eigenvectors of J z and J 2 satisfying −J ≤ m ≤ J and J ∈ [J 0 ; ns]. Therefore, for n ≥ 3 degeneracies appear (some eigenvectors |J, m are repeated), meaning that different linear combinations of elements of the local basis |m 1 , ..., m n result in eigenstates of J z and J 2 with same eigenvalue J (total spin) and m (z-component of the spin). Then, we denote by |J, m i the degenerate eigenstates of J z and J 2 where the degeneracy index i runs from 1 to l J , integer which represents th...

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Section: A Effective Amplificationmentioning

confidence: 85%

Section: Appendix G: Effective Amplificationmentioning

confidence: 97%

Section: A Effective Amplificationmentioning

confidence: 97%

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Thermodynamics from indistinguishability: Mitigating and amplifying the effects of the bath

Latune

Sinayskiy

Petruccione

2019

Phys. Rev. Research

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“…In this case, the time-dependent currents in the second law will have to be calculated numerically. We expect our findings to be relevant for systems that are coupled to reservoirs only for a finite time, e.g., in finite time thermodynamic cycles [ 52 , 53 , 54 , 55 , 56 , 57 , 58 ], where the coarse-graining dissipator is a more appropriate choice for finite-time dissipative strokes than the usual BMS limit.…”

Section: Discussionmentioning

confidence: 87%

Thermodynamics of the Coarse-Graining Master Equation

Schaller

Ablaßmayer

2020

Entropy

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We study the coarse-graining approach to derive a generator for the evolution of an open quantum system over a finite time interval. The approach does not require a secular approximation but nevertheless generally leads to a Lindblad–Gorini–Kossakowski–Sudarshan generator. By combining the formalism with full counting statistics, we can demonstrate a consistent thermodynamic framework, once the switching work required for the coupling and decoupling with the reservoir is included. Particularly, we can write the second law in standard form, with the only difference that heat currents must be defined with respect to the reservoir. We exemplify our findings with simple but pedagogical examples.

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“…With the renewed interest in quantum thermodynamics, it has become a relevant question whether QPTs can be put to use e.g. as working fluids of quantum heat engines [11][12][13][14]. This opens another broad research area of dissipative QPTs in non-equilibrium setups.…”

Section: Introductionmentioning

confidence: 99%

Polaron-transformed dissipative Lipkin-Meshkov-Glick model

Kopylov

Schaller

2019

Phys. Rev. A

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We investigate the Lipkin-Meshkov-Glick model coupled to a thermal bath. Since the isolated model itself exhibits a quantum phase transition, we explore the critical signatures of the open system. Starting from a system-reservoir interaction written in positive definite form, we find that the position of the critical point remains unchanged, in contrast to the popular mean-field prediction. Technically, we employ the polaron transform to be able to study the full crossover regime from the normal to the symmetry-broken phase, which allows us to investigate the fate of quantum-critical points subject to dissipative environments. The signatures of the phase transition are reflected in observables like stationary mode occupation or waiting-time distributions.

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Collective performance of a finite-time quantum Otto cycle

Cited by 54 publications

References 78 publications

Thermodynamics from indistinguishability: Mitigating and amplifying the effects of the bath

Thermodynamics from indistinguishability: Mitigating and amplifying the effects of the bath

Thermodynamics of the Coarse-Graining Master Equation

Polaron-transformed dissipative Lipkin-Meshkov-Glick model

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