Colloidal engines for innovative tests of information thermodynamics

Abstract

Recent theoretical developments in information thermodynamics elucidated the link between the acquired information and the entropy production through measurement and feedback control by generalizing the fluctuation theorems and the second law of thermodynamics. We summarize here our recent experimental studies based on the colloidal system that have been conducted to test the theoretical findings of information thermodynamics. In particular, we present the design principles of error-free and noisy information engines consisting of a colloidal particle in an optical trap that is capable of performing nearly error-free measurement and ultrafast feedback control. Our perspectives on future experimental studies are also presented.

Maximizing power and velocity of an information engine

“…For our macroscopic experimental apparatus, the operating costs dwarf the engine output; however, several studies have shown that the fundamental, unavoidable information costs in similar contexts can be much lower (43)(44)(45)(46)(47). In the limits of infinite sampling frequency and signal-to-noise ratio (SNR), different ways of estimating costs (24)(25)(26)48) all lead to vanishing efficiency when applied to our setup. We have not here specified the details of our feedback controller, but one reasonable choice is to allow each new measurement to overwrite the previous one.…”

Fluctuations in heat engines

“…While these machines often cannot be categorized as heat engines, the thermodynamic uncertainty relations should still limit their performance in terms of transport coefficients, their fluctuations, and transport efficiency. Of particular interest are processes driven by information [22,23,[80][81][82] and transport in systems of many interacting particles [146]. Another twist in the theory is expected for systems in contact with non-equilibrium reservoirs, where the very definitions of work and heat are still subjects of keen discussions [45,46,[147][148][149][150][151], and thus the results valid for cyclic and steady-state heat engines operating with equilibrium reservoirs cannot be taken for granted.…”

“…the role of coupling between system's internal degrees of freedom [77], many-particle gas models of a cylinder enclosed by a piston and coupled to a thermostat [78], and a system of interacting unicyclic machines undergoing a phase transition [79]. For feedback cooling techniques, the concept of fluctuating efficiency was reformulated in terms of fluctuating information flows [80][81][82]. The fluctuating efficiency was also introduced for quantum machines, see e.g.…”

“…As for experiments, to the best of our knowledge, there exist only a few works reporting measurements of efficiency fluctuations [81,82,89].…”

Dichotomous flow with thermal diffusion and stochastic resetting

“…Models of that type can be, for example, used to design optimal driving level maximizing performance of a mechanical device. Also, different variants of stochastic diffusion processes with resetting may be realized today experimentally with colloidal particles in a flow chamber 30 or optical tweezers 31 . This opens the possibility of verification tests for many theoretical investigations of resetting mechanisms, their further developments and applications.…”