Time-resolved measurement of capacitance in a Josephson tunnel junction

The capacitance of a Josephson tunnel junction is an important parameter, which determines its plasma frequency omega(p) and thus the energy level spacing in the quantum regime. When a microwave signal at the frequency of omega is applied to a current-biased junction in its zero-voltage state, the escape rate from this state is somehow enhanced. The enhancement is expected to go through a pronounced maximum when omega(p)=omega. Making use of such microwave generated resonant activation in the thermal regime, we have developed a time-resolved measurement scheme for determining the junction capacitance with an uncertainty of less than 2%. (c) 2006 American Institute of Physics.