The paper by C. Jarzynski presents a nonequilibrium equality for the free energy difference between two configurations of a classical system, derived from ensemble measurements of the work performed during finite-time parameter switching. The key result is an equality: \[ \overline{\exp - \beta W} = \exp - \beta \Delta F, \] where \(\overline{\exp - \beta W}\) is the ensemble average of the exponential of the negative work done, and \(\Delta F\) is the free energy difference. This equality holds regardless of the path and rate of parameter switching, provided the coupling to the reservoir is weak. The paper also discusses the implications of this result for numerical simulations and experimental verification, noting that it may be most applicable to systems with a moderate number of degrees of freedom, such as nanoscale systems. The equality provides a method to compute free energy differences more accurately than traditional bounds based on work averages.The paper by C. Jarzynski presents a nonequilibrium equality for the free energy difference between two configurations of a classical system, derived from ensemble measurements of the work performed during finite-time parameter switching. The key result is an equality: \[ \overline{\exp - \beta W} = \exp - \beta \Delta F, \] where \(\overline{\exp - \beta W}\) is the ensemble average of the exponential of the negative work done, and \(\Delta F\) is the free energy difference. This equality holds regardless of the path and rate of parameter switching, provided the coupling to the reservoir is weak. The paper also discusses the implications of this result for numerical simulations and experimental verification, noting that it may be most applicable to systems with a moderate number of degrees of freedom, such as nanoscale systems. The equality provides a method to compute free energy differences more accurately than traditional bounds based on work averages.