Performance bounds of non-adiabatic quantum harmonic Otto engine and refrigerator under a squeezed thermal reservoir

TL;DR

This paper investigates the efficiency limits of a quantum harmonic Otto engine and refrigerator coupled to squeezed thermal reservoirs, revealing bounds dependent solely on reservoir parameters and contrasting with previous claims of unit efficiency.

Contribution

It derives analytic bounds on efficiency and performance of a quantum Otto cycle with squeezed reservoirs, clarifying the impact of squeezing on quantum thermodynamic limits.

Findings

Maximum efficiency is 1/2, contrary to earlier claims of unit efficiency.

Derived bounds depend only on reservoir parameters, not system specifics.

Squeezing enables operational regimes for refrigerators not possible in standard cases.

Abstract

We analyze the performance of a quantum Otto cycle, employing time-dependent harmonic oscillator as the working fluid undergoing sudden expansion and compression strokes during the adiabatic stages, coupled to a squeezed reservoir. First, we show that the maximum efficiency that our engine can achieve is 1/2 only, which is in contrast with the earlier studies claiming unit efficiency under the effect of squeezed reservoir. Then, we obtain analytic expressions for the upper bound on the efficiency as well as on the coefficient of performance of the Otto cycle. The obtained bounds are independent of the parameters of the system and depends on the reservoir parameters only. Additionally, with hot squeezed thermal bath, we obtain analytic expression for the efficiency at maximum work which satisfies the derived upper bound. Further, in the presence of squeezing in the cold reservoir, we specify an operational regime for the Otto refrigerator otherwise forbidden in the standard case.