While Josephson–junction-like structures intrinsic to the layered cuprate high temperature superconductors offer an attractive stage for exploiting possible applications to new quantum technologies, the low energy quasiparticle excitations characteristically present in these $d$-wave superconductors may easily destroy the coherence required. Here we demonstrate for the first time the feasibility of macroscopic quantum tunneling in the intrinsic Josephson junctions of a high temperature superconductor ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$, and find it to be characterized by a high classic-to-quantum crossover temperature and a relatively weak quasiparticle dissipation.

• Received 29 December 2004

DOI:https://doi.org/10.1103/PhysRevLett.95.107005