Theory of macroscopic quantum tunneling in Nb/Au/YBCO Josephson junctions

We have theoretically investigated macroscopic quantum tunneling (MQT) in s-wave/d-wave (Nb/Au/YBCO) Josephson junctions, and the influence of the nodal-quasiparticle and the zero energy bound states (ZES) on MQT. In contrast to d-wave/d-wave junctions, low-energy quasiparticle excitations resulting from nodal-quasiparticles and ZES are suppressed due to the finite isotropic gap of the s-wave superconductor. Therefore, the inherent dissipation of these junctions is weak. This result suggests the high potential of s-wave/d-wave hybrid junctions for applications in quantum information devices.