TY - JOUR
T1 - Surpassing the Carnot efficiency by extracting imperfect work
AU - Ying Ng, Nelly Huei
AU - Woods, Mischa Prebin
AU - Wehner, Stephanie
PY - 2017
Y1 - 2017
N2 - 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.
AB - 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.
KW - quantum heat engines
KW - quantum thermodynamics
KW - single-shot work extraction
KW - thermodynamic resource theories
UR - http://www.scopus.com/inward/record.url?scp=85038424358&partnerID=8YFLogxK
U2 - 10.1088/1367-2630/aa8ced
DO - 10.1088/1367-2630/aa8ced
M3 - Article
AN - SCOPUS:85038424358
SN - 1367-2630
VL - 19
JO - New Journal of Physics
JF - New Journal of Physics
IS - 11
M1 - 113005
ER -