Quantum simulation of indefinite causal order induced quantum refrigeration

TL;DR

This paper demonstrates experimentally that indefinite causal order in quantum mechanics can enhance thermodynamic processes, such as heat extraction and refrigeration, surpassing classical limitations by exploiting quantum causal nonseparability.

Contribution

It introduces an experimental quantum simulation of ICO in thermodynamics, showing improved refrigeration performance through multiple ICO channel passes.

Findings

Quantum heat extraction from thermal reservoirs in ICO

Enhanced refrigeration cycle performance via multiple ICO passes

Causal nonseparability as a resource for quantum thermodynamics

Abstract

In the classical world, physical events always happen in a fixed causal order. However, it was recently revealed that quantum mechanics allows events to occur with indefinite causal order (ICO). In this study, we use an optical quantum switch to experimentally investigate the application of ICO in thermodynamic tasks. Specifically, we simulate the working system interacting with two identical thermal reservoirs in an ICO, observing the quantum heat extraction even though they are in thermal equilibrium where heat extraction is unaccessible by traditional thermal contact. Using such a process, we simulate an ICO refrigeration cycle and investigate its properties. We also show that by passing through the ICO channel multiple times, one can extract more heat per cycle and thus obtain a higher refrigeration performance. Our results suggest that the causal nonseparability can be a powerful resource for quantum thermodynamic tasks.