Macroscopic Quantum Tunneling in 1-μm Nb Josephson Junctions

Abstract

The probability distributions for switching out of the superconducting state of low-cur-rent-density 1-μm Nb Josephson junctions with capacitance ≈ 0.1 pF have been measured as a function of temperature $T$ down to 3 mK. Below 100 mK the distribution widths become independent of $T$. The results are in excellent agreement with predictions for the quantum tunneling of the (macroscopic) junction phase that include the reduction of tunneling rates due to dissipation.