Dynamical Control of Quantum Heat Engines Using Exceptional Points

TL;DR

This paper experimentally demonstrates how Liouvillian exceptional points influence the dynamics and efficiency of a quantum heat engine, revealing new control strategies for quantum thermal machines using non-Hermitian physics.

Contribution

It reports the first experimental realization of a single-ion quantum heat engine exploiting Liouvillian exceptional points to enhance performance.

Findings

Operating in different phases around the exceptional point improves work output.

Engine efficiency is higher when cycling through phases separated by the exceptional point.

Coherence and non-Hermitian effects significantly impact quantum heat engine performance.

Abstract

A quantum thermal machine is an open quantum system coupled to hot and cold thermal baths. Thus, its dynamics can be well understood using the concepts and tools from non-Hermitian quantum systems. A hallmark of non-Hermiticity is the existence of exceptional points where the eigenvalues of a non-Hermitian Hamiltonian or an Liouvillian superoperator and their associated eigenvectors coalesce. Here, we report the experimental realisation of a single-ion heat engine and demonstrate the effect of the Liouvillian exceptional points on the dynamics and the performance of a quantum heat engine. Our experiments have revealed that operating the engine in the exact- and broken-phases, separated by a Liouvillian exceptional point, respectively during the isochoric heating and cooling strokes of an Otto cycle produces more work and output power and achieves higher efficiency than executing the Otto cycle completely in the exact phase where the system has an oscillatory dynamics and higher coherence. This result opens interesting possibilities for the control of quantum heat engines and will be of interest to other research areas that are concerned with the role of coherence and exceptional points in quantum processes and in work extraction by thermal machines.