Single-Atom Verification of the Information-Theoretical Bound of Irreversibility at the Quantum Level

TL;DR

This paper presents the first theoretical prediction and experimental verification of an information-theoretical bound on entropy production in a quantum system, revealing complex dependencies and fundamental differences from classical thermodynamics.

Contribution

It introduces a quantum mechanical model and experimental validation of an information-theoretical bound on entropy production in a single-atom system.

Findings

The bound depends on drive-to-decay ratio and initial state.

Experimental verification was performed using a single trapped ion.

The results highlight fundamental differences in quantum thermodynamics.

Abstract

Quantitative measure of disorder or randomness based on the entropy production characterizes thermodynamical irreversibility, which is relevant to the conventional second law of thermodynamics. Here we report, in a quantum mechanical fashion, the first theoretical prediction and experimental exploration of an information-theoretical bound on the entropy production. Our theoretical model consists of a simplest two-level dissipative system driven by a purely classical field, and under the Markovian dissipation, we find that such an information-theoretical bound, not fully validating quantum relaxation processes, strongly depends on the drive-to-decay ratio and the initial state. Furthermore, we carry out experimental verification of this information-theoretical bound by means of a single spin embedded in an ultracold trapped $^{40}$Ca$^{+}$ ion. Our finding, based on a two-level model, is fundamental to any quantum thermodynamical process and indicates much difference and complexity in quantum thermodynamics with respect to the conventionally classical counterpart.