Short Time Cycles of Purely Quantum Refrigerators

TL;DR

This paper investigates quantum Otto refrigerator cycles operating at extremely short cycle times, revealing unique coherence effects and providing a classification scheme that simplifies analysis of their cooling performance.

Contribution

It introduces the concept of sudden quantum refrigerator cycles, analyzes their stability and coherence properties, and develops a classification scheme for their performance evaluation.

Findings

Sudden cycles reach a stable limit cycle with significant coherence.

Coherence persists due to very short equilibration times.

A classification scheme simplifies the analysis of cooling power and efficiency.

Abstract

Four stroke Otto refrigerator cycles with no classical analogue are studied. Extremely short cycle times with respect to the internal time scale of the working medium characterize these refrigerators. Therefore these cycles are termed sudden. The sudden cycles are characterized by the stable limit cycle which is the invariant of the global cycle propagator. During their operation the state of the working medium possesses significant coherence which is not erased in the equilibration segments due to the very short time allocated. This characteristic is reflected in a difference between the energy entropy and the Von Neumann entropy of the working medium. A classification scheme for sudden refrigerators is developed allowing simple approximations for the cooling power and coefficient of performance.