Models of heat machines have been historically used to study basic thermodynamic questions and establish its fundamental laws. The Carnot engine is a prime example of this approach.

That is the reason why so many groups have used models of quantum heat machines to study thermodynamic questions at the quantum level.

Several studies on quantum thermodynamics gave rise to a basic question: could a heat machine governed by quantum mechanics preform differently than its classical counterpart? The answer is yes, as shown by our group.

Classically, a volume change is required in order to extract or inject mechanical work (for a gas or liquid W = pdV).

In contrast, quantum heat machines can operate using an incompressible fluid that undergoes transformations that change the shape of the “combustion chamber” but not the volume. This effect relies on the fact that boundary effects can be neglected for macroscopic classical systems and their thermodynamic behavior mainly depends on the bulk of the system (the volume) and not the shape (related to the boundary). In contrast, for quantum systems the energy levels are highly sensitive to boundary conditions.