Phase qubits fabricated with trilayer junctions
We have developed a novel Josephson junction geometry with minimal volume of lossy isolation dielectric, suitable for higher quality trilayer junctions implemented in qubits. The junctions are based on in situ deposited trilayers with thermal tunnel oxide, have micron-sized areas and a low subgap current. In qubit spectroscopy only a few avoided level crossings are observed, and the measured relaxation time of T1≈400 ns is in good agreement with the usual phase qubit decay time, indicating low loss due to the additional isolation dielectric.