Chiral quantum heating and cooling with an optically controlled ion

TL;DR

This paper demonstrates chiral quantum heating and cooling using an ultracold ion system by dynamically encircling Liouvillian exceptional points, revealing new topological and thermodynamic phenomena in non-Hermitian quantum systems.

Contribution

It introduces the first experimental realization of chiral quantum thermodynamic cycles near Liouvillian exceptional points in a trapped ion system.

Findings

Chiral heat absorption and release observed in quantum heat engine and refrigerator.

Dynamic encircling near LEPs causes chiral thermodynamic cycles.

Landau-Zener-Stückelberg processes influence the thermodynamics during encircling.

Abstract

Quantum heat engines and refrigerators are open quantum systems, whose dynamics can be well understood using a non-Hermitian formalism. A prominent feature of non-Hermiticity is the existence of exceptional points (EPs), which has no counterpart in closed quantum systems. It has been shown in classical systems that dynamical encirclement in the vicinity of an EP, whether the loop includes the EP or not, could lead to chiral mode conversion. Here, we show that this is valid also for quantum systems when dynamical encircling is performed in the vicinity of their Liouvillian EPs (LEPs) which include the effects of quantum jumps and associated noise - an important quantum feature not present in previous works. We demonstrate, using a Paul-trapped ultracold ion, the first chiral quantum heating and refrigeration by dynamically encircling a closed loop in the vicinity of an LEP. We witness the cycling direction to be associated with the chirality and heat release (absorption) of the quantum heat engine (quantum refrigerator). Our experiments have revealed that not only the adiabaticity-breakdown but also the Landau-Zener-St\"uckelberg process play an essential role during dynamic encircling, resulting in chiral thermodynamic cycles. Our observations contributes to further understanding of chiral and topological features in non-Hermitian systems and pave a way to exploring the relation between chirality and quantum thermodynamics.