Quantumparametricoscillator heat engines in squeezed thermal baths: Foundational theoretical issues
Abstract
In this paper we examine some foundational issues of a class of quantum engines where the system consists of a single quantum parametric oscillator, operating in an Otto cycle consisting of four stages of two alternating phases: the isentropic phase is detached from any bath (thus a closed system) where the natural frequency of the oscillator is changed from one value to another, and the isothermal phase where the system (now rendered open) is put in contact with one or two squeezed baths of different temperatures, whose nonequilibrium dynamics follows the HuPazZhang (HPZ) master equation for quantum Brownian motion. The HPZ equation is an exact nonMarkovian equation which preserves the positivity of the density operator and is valid for (1) all temperatures, (2) arbitrary spectral density of the bath, and (3) arbitrary coupling strength between the system and the bath. Taking advantage of these properties we examine some key foundational issues of theories of quantum open and squeezed systems for these two phases of the quantum Otto engines. This includes (1) the nonMarkovian regimes for nonOhmic, lowtemperature baths, (2) what to expect in nonadiabatic frequency modulations, (3) strong systembath coupling, as well as (4) the proper junction conditions between these two phases. Our aim here is not to present ways for attaining higher efficiency but to build a more solid theoretical foundation for quantum engines of continuous variables covering a broader range of parameter spaces that we hope are of use for exploring such possibilities.
 Publication:

Physical Review E
 Pub Date:
 January 2022
 DOI:
 10.1103/PhysRevE.105.014108
 arXiv:
 arXiv:2106.12325
 Bibcode:
 2022PhRvE.105a4108A
 Keywords:

 Quantum Physics;
 Condensed Matter  Statistical Mechanics;
 High Energy Physics  Theory
 EPrint:
 33 pages, 2 figures