
Energy transferred by a force acting over a distance, a key output measure of an engine.Work is the energy transferred when a force moves an object over a distance. It is a core concept in physics, quantifying the effect of an engine or any mechanical process. In the context of quantum engines, work is the useful output extracted from quantum systems, often measured in terms of energy changes or power generated.
The concept was formalized by Gaspard-Gustave de Coriolis in the early 19th century, who introduced the term 'work' in mechanics.
Mechanically, work is calculated as the product of force and displacement in the direction of the force. In quantum systems, work is defined through energy changes of the system, often involving transitions between quantum states. Quantum engines operate by cycling a system through states, extracting work from quantum coherence or measurement processes.
Work is used to measure engine output in vehicles and power plants, and in quantum thermodynamics to design efficient quantum heat engines.
In quantum engines, work can be extracted from a single electron, as demonstrated in experiments with nitrogen-vacancy centers in diamond.
| dU | variable | Infinitesimal change in internal energy — internal energy joule |
| δQ | variable | Infinitesimal heat added to the system — heat joule |
| δW | variable | Infinitesimal work done by the system — work joule |
| d | operator | Exact differential of a state function — exact differential |
| δ | operator | Inexact differential for path-dependent quantities — inexact differential |








