Autonomous quantum clocks: does thermodynamics limit our ability to measure time?

TL;DR

This paper investigates the fundamental thermodynamic limits of autonomous quantum clocks, revealing a trade-off between heat dissipation and clock accuracy, and establishing entropy production as an unavoidable aspect of quantum time measurement.

Contribution

It introduces a complete, autonomous quantum clock model powered by thermal baths and analyzes how thermodynamics constrains its performance and efficiency.

Findings

Thermodynamics imposes a trade-off between heat dissipation and clock accuracy.

Fundamental entropy production is unavoidable in autonomous quantum clocks.

Quantum machines cannot achieve perfect efficiency at finite power.

Abstract

Time remains one of the least well understood concepts in physics, most notably in quantum mechanics. A central goal is to find the fundamental limits of measuring time. One of the main obstacles is the fact that time is not an observable and thus has to be measured indirectly. Here we explore these questions by introducing a model of time measurements that is complete and autonomous. Specifically, our autonomous quantum clock consists of a system out of thermal equilibrium --- a prerequisite for any system to function as a clock --- powered by minimal resources, namely two thermal baths at different temperatures. Through a detailed analysis of this specific clock model, we find that the laws of thermodynamics dictate a trade-off between the amount of dissipated heat and the clock's performance in terms of its accuracy and resolution. Our results furthermore imply that a fundamental entropy production is associated with the operation of any autonomous quantum clock, assuming that quantum machines cannot achieve perfect efficiency at finite power. More generally, autonomous clocks provide a natural framework for the exploration of fundamental questions about time in quantum theory and beyond.