Quantum simulation of indefinite causal order induced quantum refrigeration

Understand

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.