Decoherence in rf SQUID Qubits

Bennett, Douglas A.
Longobardi, Luigi
Patel, Vijay
Chen, Wei
Averin, Dmitri V.
Lukens, James E.
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We report measurements of coherence times of an rf SQUID qubit using pulsed microwaves and rapid flux pulses. The modified rf SQUID, described by an double-well potential, has independent, in situ, controls for the tilt and barrier height of the potential. The decay of coherent oscillations is dominated by the lifetime of the excited state and low frequency flux noise and is consistent with independent measurement of these quantities obtained by microwave spectroscopy, resonant tunneling between fluxoid wells and decay of the excited state. The oscillation's waveform is compared to analytical results obtained for finite decay rates and detuning and averaged over low frequency flux noise.
Comment: 24 pages, 13 figures, submitted to the journal Quantum Information Processing
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics