Thermodynamical Control by Frequent Quantum Measurements

TL;DR

This paper explores how frequent quantum measurements can drastically alter heat flow and thermalization in quantum systems, enabling rapid control of entropy and temperature beyond standard thermodynamic expectations.

Contribution

It demonstrates that frequent quantum measurements can induce Zeno or anti-Zeno effects, leading to non-standard thermodynamic behavior in quantum systems.

Findings

Frequent measurements cause deviations from expected thermal equilibrium.

Quantum Zeno and anti-Zeno effects influence entropy and temperature.

Fast control of quantum states is possible before thermalization.

Abstract

Heat flow between a large ``bath'' and a smaller system brings them progressively closer to thermal equilibrium while increasing their entropy. Deviations from this trend are fluctuations involving a small fraction of a statistical ensemble of systems interacting with the bath: in this respect, quantum and classical thermodynamics are in agreement. Can there be drastic differences between them? Here we address a distinctly quantum mechanical setting that displays such differences: disturbances of thermal equilibrium between two-level systems (TLS) and a bath by frequent and brief quantum (non-demolishing) measurements of the TLS energy-states. If the measurements are frequent enough to induce either the Zeno or the anti-Zeno regime, namely, the slowdown or speedup of the TLS relaxation, then the resulting entropy and temperature of both the system and the bath are found to be completely unrelated to what is expected by standard thermodynamical rules that hold for memoryless baths. The practical advantage of these anomalies is the possibility of very fast control of heat and entropy, allowing cooling and state-purification of quantum systems much sooner than their thermal equilibration time.