Related Experiment Video
Updated: Mar 30, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Thermodynamic universality of quantum Carnot engines
Bartłomiej Gardas1,2, Sebastian Deffner1,3
1Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Abstract:
The Carnot statement of the second law of thermodynamics poses an upper limit on the efficiency of all heat engines. Recently, it has been studied whether generic quantum features such as coherence and quantum entanglement could allow for quantum devices with efficiencies larger than the Carnot efficiency. The present study shows that this is not permitted by the laws of thermodynamics-independent of the model. We will show that rather the definition of heat has to be modified to account for the thermodynamic cost of maintaining non-Gibbsian equilibrium states. Our theoretical findings are illustrated for two experimentally relevant examples.
Related Concept Videos
The Carnot Cycle and the Second Law of Thermodynamics
Since the individual steps in a Carnot cycle can be reversed, the entire cycle is, thus, reversible. If a Carnot cycle is reversed, it becomes a Carnot refrigerator. It extracts heat Qc from a cold reservoir at...
The Carnot Cycle
What could be the theoretical limit to the efficiency of a heat engine? The...
Entropy
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
Entropy
Efficiency of The Carnot Cycle
Statements of the Second Law of Thermodynamics

