  We explore the thermodynamic geometry of a simple system that models the
bistable dynamics of nucleic acid hairpins in single molecule force-extension
experiments. Near equilibrium, optimal (minimum-dissipation) driving protocols
are governed by a generalized linear response friction coefficient. Our
analysis and simulations demonstrate that the friction coefficient of the
driving protocols is sharply peaked at the interface between metastable
regions, which leads to minimum-dissipation protocols that drive rapidly within
a metastable basin, but then linger longest at the interface, giving thermal
fluctuations maximal time to kick the system over the barrier. Intuitively, the
same principle applies generically in free energy estimation (both in steered
molecular dynamics simulations and in single-molecule experiments), provides a
design principle for the construction of thermodynamically efficient coupling
between stochastic objects, and makes a prediction regarding the construction
of evolved biomolecular motors.
