Rectification in a Stochastically Driven Three-Junction SQUID Rocking Ratchet

A three-junction SQUID forms a rocking ratchet for the phase differences across the Josephson junctions. In this Letter we investigate its capability to rectify voltages under stochastic drive currents with a white frequency spectrum up to a cutoff frequency f(cut). Experimentally, we accessed the adiabatic regime and find very good agreement with theory. Numerically, we also investigated large values of f(cut) and find, in agreement with the laws of thermodynamics, that the response disappears, as f(cut) becomes much larger than the characteristic frequency scales of the system.