Information Demons go to Vegas

Like games of chance and stocks, small physical systems are subject to fluctuations, following an unpredictable evolution. These fluctuations are not purely random, but obey universal statistical laws. In particular, information about the evolution of a thermodynamic system can be used by Maxwell’s demons to extract work using feedback control at the cost of generating information.

In their work, Gonzalo Manzano – Post Doc at IQOQI Vienna – and his international co-authors propose and realize a new concept of information demon, lacking feedback but allowed to stop a thermodynamic process using a gambling strategy. Such gambling strategy is executed at random times when a prescribed condition is satisfied. Their theory is inspired in casino games like the roulette, where players may resume or stop gambling according to some strategy, but are not allowed to modify the rules of the game using feedback. This situation is ubiquitous at small scales, where an accurate manipulation of the system of interest is often not possible.


The researchers show that, even if lacking feedback, the performance of gambling demons can bypass the limits set by the standard formulation of the second law in unexpected ways. For example, gambling demons can extract work on average beyond the free energy change, if the time-reversal symmetry of the dynamics is broken. More precisely, Manzano and his colleagues derive new fluctuation relations and second-law-like inequalities that further unveil the fundamental structure of work and entropy production in stochastic systems. The results are valid for arbitrary non-equilibrium driving and gambling strategies with finite time horizon. The researchers also extend their framework to quantum thermodynamics, where they identified the role played by coherence and quantum measurements in the gambling protocols.


They tested their results in a nano-electronic experimental setup, a single-electron box, fabricated and operated by the PICOgroup (Aalto, Finland). In the experiment, an electrostatic potential drives the dynamics of individual electrons tunneling into a metallic island, which is continuously measured by a single-electron transistor. This allows to record traces of the stochastic trajectories followed by the electrons and infer the relevant thermodynamic quantities. The experimental results reveal work extraction by single-electron gambling demons beyond the free energy change when using suitable gambling strategies. Finally, Manzano and his colleagues also confirm the breakdown of traditional fluctuation relations under gambling and the excellent agreement of experimental data with newly derived ones. These results may open new avenues in efficient energy extraction techniques at the nanoscale using optimal investment and gaming strategies.