Surpassing the Carnot efficiency by extracting imperfect work

Surpassing the Carnot efficiency by extracting imperfect work

Ng, N.H.Y. (TU Delft Quantum Information and Software; TU Delft QuTech; National University of Singapore)
Woods, M.P. (TU Delft QID/Wehner Group; TU Delft QuTech; University College London (UCL))
Wehner, S.D.C. (TU Delft Quantum Internet Division; TU Delft Quantum Information and Software; TU Delft QuTech; National University of Singapore)

QuTech

Quantum Internet Division

2017

A suitable way of quantifying work for microscopic quantum systems has been constantly debated in the field of quantum thermodynamics. One natural approach is to measure the average increase in energy of an ancillary system, called the battery, after a work extraction protocol. The quality of energy extracted is usually argued to be good by quantifying higher moments of the energy distribution, or by restricting the amount of entropy to be low. This limits the amount of heat contribution to the energy extracted, but does not completely prevent it. We show that the definition of 'work' is crucial. If one allows for a definition of work that tolerates a non-negligible entropy increase in the battery, then a small scale heat engine can possibly exceed the Carnot efficiency. This can be done without using any additional resources such as coherence or correlations, and furthermore can be achieved even when one of the heat baths is finite in size.

quantum heat engines
quantum thermodynamics
single-shot work extraction
thermodynamic resource theories

http://resolver.tudelft.nl/uuid:b5cd3624-59af-4b65-864f-d26220c9f281

https://doi.org/10.1088/1367-2630/aa8ced

1367-2630

New Journal of Physics, 19 (11)

Institutional Repository

journal article

© 2017 N.H.Y. Ng, M.P. Woods, S.D.C. Wehner