Abstract
Stability is an important property of small thermal machines with fluctuating power output. We here consider a finite-time quantum Carnot engine based on a degenerate multilevel system and study the influence of its finite Hilbert space structure on its stability. We optimize in particular its relative work fluctuations with respect to level degeneracy and level number. We find that its optimal performance may surpass those of nondegenerate two-level engines or harmonic oscillator motors. Our results show how to realize high-performance, high-stability cyclic quantum heat engines.Received 13 July 2020Accepted 13 July 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.L032041Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum thermodynamicsStatistical Physics
Highlights
The Carnot engine is one of the most emblematic examples of a thermal machine
Constancy has been established for steady-state heat engines, implying that power fluctuations diverge at maximum efficiency and finite power [27], they may remain finite for quasistatic cyclic thermal machines [28]
In this Letter, we investigate the generic features of the power fluctuations in a finite-time quantum Carnot engine in the quasistatic limit
Summary
A nondegenerate system with an arbitrary level number, and (iii) a three-level system with a generic degree of degeneracy. The system remains in a thermal state and the two finite-time processes are quasistatic In this case, the work distributions are sharp (with no fluctuations) and work is deterministic [41], P1,3(w1,3 ) = δ(w1,3 − W1,3 ). The Fano factor for work, σw2 /W , is equal to the quotient of the constancy σP2τ and the average power P = W/τ (defined over one cycle time). A finite-time quantum Carnot engine with large work output and small work output fluctuations is characterized by a large inverse coefficient of variation |W |/σw.
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