Thermodynamic limits of dynamic cooling

Abstract

We study dynamic cooling, where an externally driven two-level system is cooled via reservoir, a quantum system with initial canonical equilibrium state. We obtain explicitly the minimal possible temperature T(min)>0 reachable for the two-level system. The minimization goes over all unitary dynamic processes operating on the system and reservoir and over the reservoir energy spectrum. The minimal work needed to reach T(min) grows as 1/T(min). This work cost can be significantly reduced, though, if one is satisfied by temperatures slightly above T(min). Our results on T(min)>0 prove unattainability of the absolute zero temperature without ambiguities that surround its derivation from the entropic version of the third law. We also study cooling via a reservoir consisting of N≫1 identical spins. Here we show that T(min)∝1/N and find the maximal cooling compatible with the minimal work determined by the free energy. Finally we discuss cooling by reservoir with an initially microcanonic state and show that although a purely microcanonic state can yield the zero temperature, the unattainability is recovered when taking into account imperfections in preparing the microcanonic state.

No-go theorem for ground state cooling given initial system-thermal bath factorization

“…The analogous proof holds for any final pure state of the system. While previous studies have pointed out the unattainability of the absolute zero of in such situations151617, here we isolate the centrality of the factorization assumption, and emphasize its strong implications regarding both the underlying physics and the suitability of master-equation type computational frameworks that often assume factorization, see e.g., Ref. 11,12,13,14.…”

Quantum effects improve the energy efficiency of feedback control

“…Our framework can also be used to compare the thermodynamic efficiency of the feedback methods considered here to a variety of cooling scenarios [38,39]. Further, while our analysis focused on the energetics of a single feedback step, repeated feedback is more commonly encountered in experiment [7,8,10].…”

Transitions between refrigeration regions in extremely short quantum cycles

“…The study of quantum heat engines is motivated by the quest to understand the fundamental relation between quantum mechanics and thermodynamics [1][2][3][4]. In addition the promise of quantum technologies requires a detailed understanding of quantum devises.…”