  We demonstrate experimentally that, applying optimal protocols which drive
the system between two equilibrium states characterized by a free energy
difference $\Delta F$, we can maximize the probability of performing the
transition between the two states with a work $W$ smaller than $\Delta F$. The
second law holds only on average, resulting in the inequality $\langle W
\rangle \geq \Delta F$. The experiment is performed using an underdamped
oscillator evolving in a double-well potential. We show that with a suitable
choice of parameters the probability of obtaining trajectories with $W \le
\Delta F$ can be larger than 95%. Very fast protocols are a key feature to
obtain these results, which are explained in terms of the Jarzynski equality.
