Quantum dynamics of a d-wave Josephson junction

Here we present the direct observation of macroscopic quantum properties in an all high-criticaltemperature superconductor d-wave Josephson junction. Although dissipation caused by low-energy excitations is expected to strongly suppress macroscopic quantum effects, we demonstrate energy level quantization in our d-wave Josephson junction. The result indicates that the role of dissipation mechanisms in high-temperature superconductors has to be revised, and it may also have consequences for the class of solid-state ‘‘quiet’’ quantum bits with superior coherence time.