Such an optical cavity could be used in a quantum engine.

Max Planck Institute of Quantum Optics

A single atom inside a reflective cavity might be enough to drive a piston in a miniature, quantum version of the engine.

An essential feature of any engine is that it converts heat into work, which can then set mechanical parts in motion. For internal combustion engines, the burning gas expands and propels it. PistonAs a result, the wheels of the car or the turbine blades are set in motion. Alvaro Tejero at the University of Granada in Spain and its…