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Long-lived, radiation-suppressed superconducting quantum bit in a planar geometry

David Pappas, National Institute of Standards and Technology

(Session 6b : Friday from 1:30 - 2:00)

Abstract. We present a superconducting qubit design that is fabricated in a 2D geometry over a superconducting ground plane to enhance the lifetime. The qubit is coupled to a microstrip resonator for readout. The circuit is fabricated on a silicon substrate by the use of low loss, stoichiometric titanium nitride for capacitor pads and small, shadow-evaporated aluminum/aluminum-oxide junctions. We observe qubit relaxation and coherence times (T1 and T2) of 11.7  0.2 s and 8.7 0.3 s, respectively. Calculations show that the proximity of the superconducting plane suppresses the otherwise high radiation loss of the qubit. A significant increase in T1 is projected for a reduced qubit-to-superconducting plane separation.