Quantum refrigerators in finite-time cycle duration

TL;DR

This paper analyzes the performance and fluctuations of a quantum Otto refrigerator operating in finite-time cycles, highlighting the trade-offs between efficiency and variability using an exactly solvable two-level system model.

Contribution

It provides an explicit analytical calculation of the cooling rate, coefficient of performance, and their variances for a finite-time quantum Otto engine, elucidating the impact of cycle durations.

Findings

Finite-time durations affect the performance and fluctuations of the quantum refrigerator.

There is a trade-off between efficiency and variance, with higher performance leading to increased fluctuations.

Analytical expressions are derived for a two-level system model.

Abstract

We derive cooling rate and coefficient of performance as well as their variances for a quantum Otto engine proceeding in finite-time cycle period. This machine consists of two driven strokes, where the system isolated from the heat reservoir undergoes finite-time unitary transformation, and two isochoric steps, where the finite-time system-bath interaction durations take the system away from the equilibrium even at the respective ends of the two stages. We explicitly calculate the statistics of cooling rate and coefficient of performance for the machine operating with an analytically solvable two-level system. We clarify the role of finite-time durations of four processes on the machine performance. We show that there is the trade-off between the performance parameter and its corresponding variance, thereby indicating that the cooling rate or coefficient of performance can be enhanced, but at the cost of increasing the corresponding fluctuations.