https://phys.org/news/2018-07-qubits-valves-quantum.html

"We have realised a miniature heat valve in a quantum system composed of an artificial atom, a superconducting qubit—the basic building block of both quantum computing and quantum heat engines," explains Professor Pekola.

In quantum computers, the qubit has to be decoupled from the noisy external world to sustain a fragile quantum state, but in quantum heat engines, the system needs to be coupled to its dissipative surroundings in the form of heat baths. A particularly puzzling problem is the process of thermalisation when connecting external heat sources or 'thermal baths' to a coherent quantum system or qubit. Ultimately, heat is exchanged between these systems through the emission of photons.