Role of the superposition principle for enhancing the efficiency of the   quantum-mechanical Carnot engine
  A role of the superposition principle is discussed for the quantum-mechanical Carnot engine introduced by Bender, Brody, and Meister [J. Phys. A 33, 4427 (2000)]. It is shown that the efficiency of the engine can be enhanced by superposition of quantum states. A finite-time process is also discussed, and the condition of the maximum power output is presented. Interestingly, the efficiency at the maximum power is lower than that without superposition. 
Sumiyoshi Abe and Shinji Okuyama (Mie University)
cond-mat.stat-mech quant-ph