Improving noisy free-energy measurements by adding more noise

TL;DR

This paper proposes a counterintuitive method of adding noise to overdamped Langevin systems to improve the accuracy of free-energy difference estimates, demonstrated through simulations.

Contribution

It introduces a novel approach of adding noise and rescaling potential energy to enhance free-energy measurement precision without altering thermodynamics.

Findings

Adding noise reduces work fluctuations and dissipated work.

The method improves convergence of free-energy estimates in simulations.

Applicability is limited to systems with controllable potential energy.

Abstract

Estimating free-energy differences using nonequilibrium work relations, such as the Jarzynski equality, is hindered by poor convergence when work fluctuations are large. For systems governed by overdamped Langevin dynamics, we propose the counterintuitive approach of adding noise in order to increase the precision of such calculations. By introducing additional stochastic fluctuations to the system and rescaling its potential energy, we leave the thermodynamics of the system unchanged while increasing its relaxation rate. For a given time-dependent protocol this modification reduces dissipated work, leading to more accurate free-energy estimates. We demonstrate this principle using computer simulations applied to two model systems. However, the regime of applicability of this strategy is likely limited, because it requires control of the system's potential energy in a way that is feasible in only a few experimental settings.