Detecting heat leaks with trapped ion qubits

TL;DR

This paper demonstrates how passivity-based frameworks, global passivity and passivity deformation, can detect hidden heat leaks in trapped ion qubits, even when the second law of thermodynamics appears to fail.

Contribution

The work experimentally applies passivity frameworks to identify unobserved environmental couplings in quantum systems, advancing quantum thermodynamics detection methods.

Findings

Global passivity detects heat leaks where second law appears violated.

Passivity deformation is more sensitive, detecting heat leaks missed by global passivity.

Experimental validation with trapped-ion qubits confirms theoretical predictions.

Abstract

Recently, the principle of \textit{passivity} has been used to set bounds on the evolution of a microscopic quantum system with a thermal initial state. In this work, we experimentally demonstrate the utility of two passivity based frameworks: global passivity and passivity deformation, for the detection of a "hidden" or unaccounted environment. We employ two trapped-ion qubits undergoing unitary evolution, which may optionally be coupled to an unobserved environment qubit. Evaluating the measurement data from the system qubits, we show that global passivity can verify the presence of a coupling to an unobserved environment - a heat leak - in a case where the second law of thermodynamics fails. We also show that passivity deformation is even more sensitive, detecting a heat leak where global passivity fails.