Analog of a quantum heat engine using a single-spin qubit

Thermodynamics was originally developed for classical many-particle systems, but recently it is being applied for the description of individual quantum systems. What essentially distinguishes the working medium of a quantum heat engine from a classical one is the ability to be in a coherent superposition of its states. In this way, the study of superpositional interference phenomena in prototypical quantum heat engines is important. The simplest realization of a quantum heat machine would be a two-level system.

Our system – a single-spin qubit based on impurities in a silicon transistor – has unique degrees of quantum control at the relatively "high" temperature of 1.6 K. By fine-tuning voltages (macroscopic parameters) we can prepare and read-out any desirable state of our individual quantum system. We demonstrated that, while being properly driven, such single-spin qubit experiences cycles analogous to the ones of an Otto heat engine; but now, importantly, displaying quantum superposition. [1]


[1] K. Ono, S. N. Shevchenko, T. Mori, S. Moriyama, F. Nori, Phys. Rev. Lett. 125, 166802 (2020). Editors' Suggestion.