Physics Department -  How to Win over the Second Law of Thermodynamics: Action of a Gambling Demon  

Abstract
The bicentennial-old Second Law of thermodynamics ensures that, when averaged over many trajectories, the mean work on the system cannot be less than the free energy change, i.e., <W> ≧ΔF. On the other hand, the breakthrough in non-equilibrium statistical mechanics and fluctuation relations in the last few decades revealed that on the trajectory level, it is possible to have Second Law violating rare events with W  <  ΔF, where W denotes the work done for a single trajectory realization. By exploiting information of the system and implementing appropriate feedback control, such as in Maxwell's demon paradigm and information engines, useful work can be extracted from the system, demonstrating the paradoxical violation of the macroscopic Second Law. In the talk, I will give a brief overview of the progress in non-equilibrium statistical physics in the past few decades. I will also discuss my recent work on manipulating Brownian particles and the issue of violating the Second Law of Thermodynamics on the trajectory level. The ability of a gambling demon to extract work with a prescribed stopping threshold of cumulative work is analyzed theoretically and realized experimentally in the paradigm system of a Brownian particle in a time-dependent squeezing potential. The mechanism by which the demon beats the Second Law of Thermodynamics (achieving  <W>  less than ΔF, or winning) is elucidated in detail by analyzing the statistics of the stopped trajectories. The obtained insights, together with the associated non-equilibrium properties, further lead to improved strategies of time-dependent stopping threshold to enhance the winning profit, which is confirmed experimentally. The associated stopping-time fluctuation relation for the gambling demon is also discussed.