Zero-Friction Quantum Engine...

Scientists have devised a way to run a quantum cycle based on the use of quantum shortcuts to adiabaticity, where friction-like effects are quenched. Shown are the four steps of a quantum Otto cycle, where heat enters (exits) the working medium and those where work is performed by (done onto).
Credit: A. del Campo, et al. ©2014 Nature Scientific Reports

(Phys.org) —In real physical processes, some energy is always lost any time work is produced. The lost energy almost always occurs due to friction, especially in processes that involve mechanical motion. But in a new study, physicists have designed an engine that operates with zero friction while still generating power by taking advantage of some quantum shortcuts.

The laws of thermodynamics successfully describe the concepts of work and heat in a wide variety of systems, ranging from refrigerators to black holes, as long as the systems are macroscopic. But for quantum technologies on the micro- and nano-scale, quantum fluctuations that are insignificant on large scales start to become prominent. As previous research as shown, the large quantum effects call for a complete reformulation of the thermodynamics laws.

What a quantum version of thermodynamics might look like is not yet known, and neither are the limitations or possible advantages of the quantum devices that would be described by such laws. However, one intriguing question is whether it may be possible to build a reversible quantum engine—one in which the engine's operation can be reversed without energy dissipation (an "adiabatic" process *).

In the new paper, the physicists have shown one example of a quantum engine that is "super-adiabatic." That is, the engine uses quantum shortcuts to achieve a state that is usually achieved only by slow adiabatic processes. This engine can achieve a state that is fully frictionless; in other words, the engine reaches its maximum efficiency, while still generating some power.

* See:

Hyper Physics: Adiabatic Processes
Princeton Wiki: Adiabatic process

Phys.org: Physicists design zero-friction quantum machine