Refrigeration by Quantum Measurements

Naghi Behzadi

Abstract We introduce two types of thermodynamic refrigeration cycles obtained through modification of the Otto cycle refrigerator by a generalized measurement channel. These refrigerators are corresponding to the activation of the measurement-based stroke before (first type) and after (second type) the full thermalization of the cooling medium by the cold reservoir in the related familiar Otto cycle. We show that the coefficient of performance for the first type modified refrigerator increases linearly in terms of measurement strength parameter, beyond the classical cooling of the familiar Otto cycle refrigerator. The second type interestingly introduces an autonomous refrigerator whose supplying work is provided by a quantum engine induced by the measurement channel and operates simultaneously inside the modified cycle. By the considered measurement channel, we also establish such modifications on the swap refrigerator. It is observed that the thermodynamic properties of the obtained modified swap refrigerators are the same as of the modified Otto cycle ones respectively.

Kassius Kohvakka

Soumyajit Mandal

Bibek Bhandari, Robert Czupryniak, Paolo Andrea Erdman +1 more

We investigated coupled-qubit-based thermal machines powered by quantum measurements and feedback. We considered 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 contact with a hot and cold bath. In the quantum Maxwell's demon case, we discuss both discrete and continuous measurements. We found that the power output from a single qubit-based device can be improved by coupling it to the second qubit. We further found 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 used continuous measurement and unitary operations to power the coupled-qubit-based refrigerator. We found that the cooling power of a refrigerator operated with swap operations can be enhanced by performing suitable measurements.

Jelena Stajic

Physics How thermodynamics works at a scale where quantum rules apply has fascinated many physicists. Buffoni et al. propose an intriguing scheme for making a tiny refrigerator that exploits the laws of quantum mechanics. Their refrigerator consists of two qubits that were initially in contact with reservoirs at different temperatures. In a refrigeration cycle, the qubits first underwent a quantum measurement, which changed their state and caused them to exchange energy with the measurement apparatus; the cycle was closed by putting the qubits back in contact with their respective reservoirs, giving away more heat than they received. The researchers predict that the procedure is robust with respect to experimental noise and may be realizable with superconducting qubits. Phys. Rev. Lett. 122 , 070603 (2019).

Galina A. Nemova