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Superconducting quantum heat engines and refrigerators

Periodic Reporting for period 3 - SQH (Superconducting quantum heat engines and refrigerators)

Reporting period: 2020-10-01 to 2022-03-31

Today, quantum heat engines are being actively studied on the theoretical level. So far, however, there hasn’t been any success in producing devices that actually utilise quantum thermodynamics and quantum phenomena. In the "Superconducting quantum heat engines and refrigerators (SQH)" project, we aim to construct quantum heat engines and refrigerators, and study whether their efficiency and cooling power can be improved in a controlled way with the help of quantum phenomena. At the same time, we will obtain information about thermodynamic phenomena in real-life quantum systems. In these studies, we utilize the state-of-the-art nanofabrication and measurement facilities of the national OtaNano research infrastructure, coordinated by the principal investigator.

Quantum technology field is currently undergoing a massive revolution as quantum phenomena are gradually shifting from research environments into new technologies and eventually into commercial use. Possible future applications of these technologies include highly sensitive sensors for industry or medical imaging as well as quantum computing and simulations that open up completely new possibilities, for example, in the development of materials for the energy sector and pharmaceutical industry. SQH research will play a key role in the control of future applications for quantum phenomena. The results could also have impact in areas such as controlling the energy consumption of electronic devices.
Our work in SQH builds on theoretical investigation of basic superconducting quantum heat engines and refrigerators. We have found strategies to achieve full capacity of a so called quantum Otto refrigerator. Also, we have initiated investigations to address fluctuating properties of energy transfer in the studied system. In parallel, we have managed to measure and theoretically analyse an experiment where heat is released to the surrounding reservoir by a quantum bit (work published in Nature Physics).

We have developed an ultra-sensitive thermometer and superconducting quantum circuit configuration for future Otto refrigerator experiments. We have demonstrated the potential of this detector to measure single microwave photons. Work on implementing amplifiers and measurements to achieve the projected energy resolution is in progress.
SQH presents a serious effort to investigate experimentally open quantum systems from the point of view of thermodynamics. It brings the classical field of research, thermodynamics, to the quantum regime,
where experiments are in their infancy. Beyond the direct fundamental significance of this endeavor, the outcome of the project will technologically benefit the performance of both current and novel devices that is often limited by our present understanding of the underlying quantum phenomena and the characteristics of open quantum systems.
Artistic illustration: measurement of heat in a quantum system