Measurement of Environmental Impedance at Plasma Frequency of Josephson Junction With Microwave Enhanced Thermal Escape

We have developed a simple and accurate method to determine the environmental impedance seen by a phase qubit at the plasma frequency of the junction by comparing the measured and simulated thermal escape rate in strong microwave field at 4.2 K. The results show that for our sample 1/Re[Y(omega)] is about 2.5 kOmega, where Re[Y(omega)] is the real part of the frequency-dependent environmental admittance.