We have measured the subgap current at 0.8 K in several hysteretic 1.5×1.6 and 2.6×2.6μm2NbAlOxNb tunnel junctions. In zero magnetic field, the critical current Ic8μA and the subgap resistance R0.3MΩ. When we apply a magnetic field, Ic can be as low as 1 nA, and R is larger than 1 GΩ. This means that in a superconducting qubit made using Nb tunnel junctions, the decoherence rate from the quasiparticle conductance may be as low as 1(100μs).

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