We demonstrate a planar, tunable superconducting qubit with energy relaxationtimes up to 44 microseconds. This is achieved by using a geometry designed toboth minimize radiative loss and reduce coupling to materials-related defects.At these levels of coherence, we find a fine structure in the qubit energylifetime as a function of frequency, indicating the presence of a sparsepopulation of incoherent, weakly coupled two-level defects. This is supportedby a model analysis as well as experimental variations in the geometry. Our`Xmon' qubit combines facile fabrication, straightforward connectivity, fastcontrol, and long coherence, opening a viable route to constructing achip-based quantum computer.
展开▼
