Bias dependence of Al/AlOx Josephson phase diffusion resistance

We perform noise-optimized dc transport measurements on test qubit Josephson junctions in order to extract critical parameters that may affect transmon decoherence. We observe a large resistance at low bias (in the nominally zero resistance state) that increases with decreasing junction size. We analyze this low bias resistance as a function of the current bias, and describe our results in terms of phase diffusion with Josephson energy and charging energy extracted directly from the current-voltage measurements. We orient our findings in the context of what role dissipation and charge noise might play in a larger transmon structure.