Characterizing autonomous Maxwell demons

Abstract

We distinguish traditional implementations of autonomous Maxwell demons from related linear devices that were recently proposed, not relying on the notions of measurements and feedback control. In both cases a current seems to flow against its spontaneous direction (imposed, e.g., by a thermal or electric gradient) without external energy intake. However, in the latter case, this current inversion may only be apparent. Even if the currents exchanged between a system and its reservoirs are inverted (by creating additional independent currents between system and demon), this is not enough to conclude that the original current through the system has been inverted. We show that this distinction can be revealed locally by measuring the fluctuations of the system-reservoir currents.

One-particle engine with a porous piston

“…Energy is dissipated because once the load mass is removed from the system one does not take away merely the potential energy gained during the process, but also any kinetic energy that the load mass happens to have at that instant. This reset operation amounts to a symmetry breaking 34 , 35 , and as with engines in which an autonomous agent ultimately has to discard heat to a low temperature reservoir 17 , in this case the mechanical agent that places the new, low-energy load masses with zero kinetic energy, acts as a low temperature reservoir at in the sense that it takes away all the kinetic energy from them. In addition, we chose to use a feedback control by unhooking and hooking a new load mass when the piston passes through positions a and b respectively.…”

“…Currently, there is a growing interest in automating the process by which a small out-of-equilibrium system like Szilard's engine generates work, by replacing a demon that acquires and processes information by an autonomous agent which is coupled to the system [14][15][16] . The second law of thermodynamics still holds in such schemes, as the autonomous agent has to be coupled to a thermal reservoir at a temperature which is lower than the lowest temperature in the system 17 .…”

Charge, spin, and heat shot noises in the absence of average currents: Conditions on bounds at zero and finite frequencies

“…We envision that the general concept of zero-current nonequilibrium noise could be developed into a versatile diagnostic tool for probing, e.g., superconducting devices, strongly correlated electron circuits [29,64] or small-scale quantum thermodynamical machines working in the absence of average heat transfer [65][66][67][68][69][70]. Of particular use is the strong dependence of the noise on temperature gradients or spin imbalances.…”

From a feedback-controlled demon to an information ratchet in a double quantum dot

“…Autonomous demons can be also be driven by temperature differences (see Refs. [52,53] and references therein), but in the present work we focus on autonomous models driven by information reservoirs.…”