Driven quantum harmonic oscillators: A working medium for thermal machines

Abstract

The study of quantum thermodynamics is key to the development of quantum thermal machines. In contrast to most of the previous proposals based on discrete strokes, here we consider a working substance that is permanently coupled to two or more baths at different temperatures and continuously driven. To this end, we investigate parametrically driven quantum harmonic oscillators coupled to heat baths via a collision model. Using a thermodynamically consistent local master equation, we derive the heat flows and power of the working device, which can operate as an engine, refrigerator, or accelerator, and analyze the instantaneous and average efficiencies and coefficients of performance. Studying the regimes of both slow and fast driving of the system, we find that an increased driving frequency can lead to a change of functioning to a dissipator. Finally, we investigate the effect of squeezing one of the thermal baths: it leads to an apparent higher efficiency compared to the corresponding Carnot value of an equilibrium bath with the same temperature and to sustained entanglement between the working substance oscillators in the limit cycle.

Cooling through parametric modulations and phase-preserving quantum measurements

“…To this end, we consider a scenario of performing multiple cycles of cooling, while the quantum oscillator is undergoing collisional interactions with the reservoir modes. Following [50], we model these interactions with the reservoir using an adiabatic Markovian master equation, resulting in the following dynamical equations for the first and second moments [50],…”

Exploiting coherence for quantum thermodynamic advantage

“…For conventional system-reservoir models with a large continuum of modes, injecting coherence may become technically onerous [34]. A more versatile alternative that may lower these practical limitations is offered by quantum collision models (CMs) [11,[66][67][68][69][70][71][72][73][74]. Because of the simplicity of their mechanism, they are well-qualified to address the thermodynamics of coherent engineered reservoirs [75][76][77].…”

Quantum Collision Models: A Beginner Guide

“…Collision models were first conceived in [ 24 ], and since then they have been used to describe a large number of physical situations: Markovian [ 25 ] and non-Markovian [ 26 , 27 , 28 , 29 , 30 ] dynamics, the role of correlations between system and environment [ 31 , 32 , 33 , 34 ], global vs local master equations [ 35 ], heat exchange and work extraction in quantum thermodynamics [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ], quantum optics [ 43 , 44 , 45 ], cascaded systems [ 46 , 47 , 48 , 49 , 50 ] and many others [ 51 ].…”