How coherent are Josephson junctions?

Around the world, there are numerous different physical systems being developed in the quest to build quantum machines and perhaps one day a large-scale quantum information processor. Quantum electrical circuits based on Josephson junctions are one of the leading solid-state candidates. These systems have made remarkable progress in the past decade, and are a particular specialty here at Yale. One of the main technical challenges is whether such devices can attain a sufficient level of coherence. I will present the results of recent experiments on a very simple realization of a superconducting quantum bit, which has improved the state of the art for the coherence times by a large (~ 20x) factor, and let us probe the dissipation, stability, and the physics of decoherence in a Josephson junction with unprecedented precision. These experiments suggest that quantum circuits should be able to reach the quantum error correction threshold, allowing the construction of large scale quantum machines.