Absolute Dynamical Limit to Cooling Weakly-Coupled Quantum Systems

TL;DR

This paper establishes a fundamental limit on cooling weakly-coupled quantum systems based on control speed, providing an optimal protocol and explicit bounds for the cooling process.

Contribution

It introduces a globally optimal control protocol for cooling quantum systems and derives explicit limits imposed by control speed in the weak coupling regime.

Findings

Derived explicit bounds on cooling limits due to control speed

Proposed a control protocol that is globally optimal

Provided numerical evidence supporting the optimality

Abstract

Cooling of a quantum system is limited by the size of the control forces that are available (the "speed" of control). We consider the most general cooling process, albeit restricted to the regime in which the thermodynamics of the system is preserved (weak coupling). Within this regime, we further focus on the most useful control regime, in which a large cooling factor, and good ground-state cooling can be achieved. We present a control protocol for cooling, and give clear structural arguments, as well as strong numerical evidence, that this protocol is globally optimal. From this we obtain simple expressions for the limit to cooling that is imposed by the speed of control.