How to break refrigeration limits using quantum superpositions of causal order

Aaron Goldberg
Research Officer (Associate),
National Research Council, Ottawa ON,
Photonic Quantum Information Processing,
Security and Disruptive Technologies

Abstract

Quantum technologies demand pure quantum states. One way to purify quantum systems is by extreme refrigeration: First, place the quantum system in a cold location such as a cryostat until it reaches thermal equilibrium with the ambient material. Then, shuttle energy and entropy from the system to an external heat bath using a sophisticated compression routine. However, this latter process, known as heat bath algorithmic cooling, has fundamental limitations to how much purification it can induce. We show how to break this process into two steps A and B, use a device known as a quantum switch to perform these two steps in a superposition of their orders A-then-B and B-then-A, and herald the presence of perfectly purified quantum systems. This is but the tip of the iceberg of promising applications introduced by the recently developed quantum switch, which may ultimately be useful for quantum communication, quantum sensing, and beyond.