Efficiency of a Brownian information machine

TL;DR

This paper analyzes the efficiency and power of a Brownian information machine that extracts work from a heat bath using feedback control, focusing on how cycle time and measurement precision affect performance.

Contribution

It provides a detailed analysis of how different control strategies influence the efficiency and power of a Brownian information machine, including optimal control of trap stiffness.

Findings

Controlling only the trap center yields zero efficiency at maximum power.

Optimal control of trap stiffness bounds efficiency between 1/2 and 1.

Perfect measurements can achieve 100% efficiency even at finite cycle times.

Abstract

A Brownian information machine extracts work from a heat bath through a feedback process that exploits the information acquired in a measurement. For the paradigmatic case of a particle trapped in a harmonic potential, we determine how power and efficiency for two variants of such a machine operating cyclically depend on the cycle time and the precision of the positional measurements. Controlling only the center of the trap leads to a machine that has zero efficiency at maximum power whereas additional optimal control of the stiffness of the trap leads to an efficiency bounded between 1/2, which holds for maximum power, and 1 reached even for finite cycle time in the limit of perfect measurements.