Universal Bounds for Fluctuations in Small Heat Engines

Ito, Kosuke; Jiang, Chao; Watanabe, Gentaro

doi:10.48550/arxiv.1910.08096

Cited by 12 publications

(22 citation statements)

References 44 publications

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“…Motivated by the experimental realization of microscopic heat engines and the theoretical advances in thermodynamics of small systems, there is a surge of activity on the study of microscopic heat engines [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Recently, fluctuations of the performance of microscopic heat engines and characterization of their performance beyond the mean values of thermodynamic quantities starts to be an active research topic [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49].…”

mentioning

confidence: 99%

“…In these studies, fluctuations of the thermodynamic quantities usually include only the intracycle correlation. In the quasistatic limit, since the thermal noise erases the correlation among thermodynamic quantities in different cycles [13,38], it is sufficient to describe the fluctuations focusing on a single cycle. However, to get the nonzero power output, we need to operate engines in a finite cycle period.…”

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confidence: 99%

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Correlation-enhanced Stability of Microscopic Cyclic Heat Engines

Xu,

Watanabe

2021

Preprint

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confidence: 99%

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confidence: 99%

Correlation-enhanced Stability of Microscopic Cyclic Heat Engines

Xu,

Watanabe

2021

Preprint

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“…Higher order efficiencies as introduced in Ref. [48] can be obtained from higher order moments of work and heat. Also a fluctuating efficiency, W/Q, can in principle be determined [49], but will not be considered here.…”

Section: Diagnostic Means Ii: Repeated Contactsmentioning

confidence: 99%

Monitoring quantum Otto engines

Son,

Talkner,

Thingna

2021

Preprint

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Unlike classical systems, a measurement performed on a quantum system always alters its state. In this work, the impacts of two diagnostic schemes to determine the performance of quantum Otto heat engines are compared: In one scheme the energy of the engine's working substance is measured after each stroke (repeated measurements) and in the other one the energies after each stroke are recorded in one or two pointer states and measured only after the completion of a prescribed number of cycles (repeated contacts). A single pointer state suffices if one is only interested in either work or heat. For a joint work and heat diagnostics two pointers are needed. These schemes are applied to Otto engines, whose working substance consists of a two-level system. Depending on the engine protocol, the duration of a single cycle may be infinite or finite. Because in the repeated contact scheme the number of measurements is drastically reduced compared to the repeated measurement scheme, the quantum coherence after, but also during the contact diagnostics is much better maintained as compared to repeated measurements which destroy any coherence at the end of each stroke. We demonstrate that maximum power, reliability, and efficiency of the engine in presence of repeated contacts typically outperform these figures of merit of repeated measurements. Due to the improved coherence persistence, heat engines with a finite cycle duration require a larger number of cycles to reach a periodically asymptotic state. Overall, our results document the importance of taking into account the particular nature of diagnostic tools for monitoring and testing purposes but also for feedback control, both in theory and experiment.

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“…For reversible heat engines under quasistatic operations, thermodynamics provides the celebrated Carnot bound on their efficiency, and some universal relations are also known even for fluctuations [38]. However, in the practical situations, heat engines are operated within a finite period of cycle.…”

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Finite-Time Thermodynamics of Fluctuations in Microscopic Heat Engines

Watanabe,

Minami

2021

Preprint

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Fluctuations of thermodynamic quantities become nonnegligible and play an important role when the system size is small. We develop finite-time thermodynamics of fluctuations in microscopic heat engines whose environmental temperature and mechanical parameter are driven periodically in time. This formalism universally holds in coarse-grained time scale whose resolution is much longer than the correlation time of the fluctuations, and is shown to be consistent with the relation analogous to the fluctuation-dissipation relation. Employing a geometric argument, a scenario to simultaneously minimize both the average and fluctuation of the dissipation in the Carnot cycle is identified. Furthermore, we demonstrate our optimized protocol can improve the dissipation and its fluctuation over the current experiment.

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Universal Bounds for Fluctuations in Small Heat Engines

Cited by 12 publications

References 44 publications

Correlation-enhanced Stability of Microscopic Cyclic Heat Engines

Correlation-enhanced Stability of Microscopic Cyclic Heat Engines

Monitoring quantum Otto engines

Finite-Time Thermodynamics of Fluctuations in Microscopic Heat Engines

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