Strong system-bath coupling reshapes characteristics of quantum thermal machines

Abstract

We study the performance of quantum absorption refrigerators, paradigmatic autonomous quantum thermal machines, and reveal central impacts of strong couplings between the working system and the thermal baths. Using the reaction coordinate quantum master equation method, which treats system-bath interactions beyond weak coupling, we discover that reshaping of the window of performance is a central outcome of strong system-bath couplings. This alteration of the cooling window stems from the dominant role of parameter renormalization at strong couplings. We further show that strong coupling admits direct transport pathways between the thermal reservoirs. Such beyond-second-order transport mechanisms are typically detrimental to the performance of quantum thermal machines. Our study reveals that it is inadequate to claim for either a suppression or an enhancement of the cooling performance at strong coupling-when analyzed against a single parameter and in a limited domain. Rather, a comprehensive approach should be adopted so as to uncover the reshaping of the operation window.

Improving the efficiency of open-quantum-system simulations using matrix product states in the interaction picture

“…In the regime of strong system-bath coupling and high temperatures, the speedup can be as large as three orders of magnitude. The approach developed here is especially promising to simulate the dynamics of open quantum systems in the high-temperature and strong-coupling regimes [1].…”

Improved Efficiency of Open Quantum System Simulations Using Matrix Products States in the Interaction Picture

“…In the regime of strong system-bath coupling and high temperatures, the speedup can be as large as 3 orders of magnitude. The approach developed here is especially promising to simulate the dynamics of open quantum systems in the high-temperature and strong-coupling regimes [1].…”