A Quantum Fluctuation Theorem
  We consider a quantum system strongly driven by forces that are periodic in time. The theorem concerns the probability $P(e)$ of observing a given energy change $e$ after a number of cycles. If the system is thermostated by a (quantum) thermal bath, $e$ is the total amount of energy transferred to the bath, while for an isolated system   $e$ is the increase in energy of the system itself. Then, we show that $P(e)/P(-e)=e^{\beta e}$, a parameter-free, model-independent relation. 
Jorge Kurchan (P.M.M.H. Ecole Sup\'erieure de Physique et Chimie   Industrielles)