Measurement-based quantum thermal machines with feedback control

TL;DR

This paper explores quantum thermal machines using coupled qubits, demonstrating how measurement strategies and feedback can enhance power output and cooling efficiency in quantum refrigerators and Maxwell's demon setups.

Contribution

It introduces measurement-based feedback control in coupled-qubit thermal machines, showing improvements in power and cooling through joint measurements and feedback strategies.

Findings

Coupling two qubits increases power output compared to single-qubit devices.

Simultaneous measurements of both qubits yield higher heat extraction than separate measurements.

Measurement-assisted operations enhance the cooling power of quantum refrigerators.

Abstract

We investigate coupled-qubit-based thermal machines powered by quantum measurements and feedback. We consider two different versions of the machine: 1) a quantum Maxwell's demon where the coupled-qubit system is connected to a detachable single shared bath, and 2) a measurement-assisted refrigerator where the coupled-qubit system is in contant with a hot and cold bath. In the quantum Maxwell's demon case we discuss both discrete and continuous measurements. We find that the power output from a single qubit-based device can be improved by coupling it to the second qubit. We further find that the simultaneous measurement of both qubits can produce higher net heat extraction compared to two setups operated in parallel where only single-qubit measurements are performed. In the refrigerator case, we use continuous measurement and unitary operations to power the coupled-qubit-based refrigerator. We find that the cooling power of a refrigerator operated with swap operations can be enhanced by performing suitable measurements.