  The free energy of glasses cannot be estimated using thermodynamic
integration, as glasses are intrinsically not in equilibrium. We present
numerical simulations showing that, in contrast, plausible free-energy
estimates of a Kob-Andersen glass can be obtained using the Jarzynski relation.
Using the Jarzynski relation, we also compute the chemical potential difference
of the two components of this system, and find that, in the glassy regime, the
Jarzynski estimate matches well with the extrapolated value of the supercooled
liquid. Our findings are of broader interest as they show that the Jarzynski
method can be used under conditions where the thermodynamic integration
approach, which is normally more accurate, breaks down completely. Systems
where such an approach might be useful are gels and jammed, glassy structures
formed by compression.
