TY - JOUR
T1 - Virtual qubits, virtual temperatures, and the foundations of thermodynamics
AU - Brunner, Nicolas
AU - Linden, Noah
AU - Popescu, Sandu
AU - Skrzypczyk, Paul
PY - 2012/5/14
Y1 - 2012/5/14
N2 - We argue that thermal machines can be understood from the perspective of "virtual qubits" at "virtual temperatures": The relevant way to view the two heat baths which drive a thermal machine is as a composite system. Virtual qubits are two-level subsystems of this composite, and their virtual temperatures can take on any value, positive or negative. Thermal machines act upon an external system by placing it in thermal contact with a well-selected range of virtual qubits and temperatures. We demonstrate these claims by studying the smallest thermal machines. We show further that this perspective provides a powerful way to view thermodynamics, by analyzing a number of phenomena. This includes approaching Carnot efficiency (where we find that all machines do so essentially by becoming equivalent to the smallest thermal machines), entropy production in irreversible machines, and a way to view work in terms of negative temperature and population inversion. Moreover we introduce the idea of "genuine" thermal machines and are led to considering the concept of "strength" of work.
AB - We argue that thermal machines can be understood from the perspective of "virtual qubits" at "virtual temperatures": The relevant way to view the two heat baths which drive a thermal machine is as a composite system. Virtual qubits are two-level subsystems of this composite, and their virtual temperatures can take on any value, positive or negative. Thermal machines act upon an external system by placing it in thermal contact with a well-selected range of virtual qubits and temperatures. We demonstrate these claims by studying the smallest thermal machines. We show further that this perspective provides a powerful way to view thermodynamics, by analyzing a number of phenomena. This includes approaching Carnot efficiency (where we find that all machines do so essentially by becoming equivalent to the smallest thermal machines), entropy production in irreversible machines, and a way to view work in terms of negative temperature and population inversion. Moreover we introduce the idea of "genuine" thermal machines and are led to considering the concept of "strength" of work.
U2 - 10.1103/PhysRevE.85.051117
DO - 10.1103/PhysRevE.85.051117
M3 - Article (Academic Journal)
C2 - 23004713
SN - 1539-3755
VL - 85
SP - -
JO - Physical Review E: Statistical, Nonlinear, and Soft Matter Physics
JF - Physical Review E: Statistical, Nonlinear, and Soft Matter Physics
IS - 5
M1 - 051117
ER -