Decoherence in rf SQUID Qubits

Abstract

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.

24 pages, 13 figures, submitted to the journal Quantum Information Processing

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• Correlated flux noise and decoherence in two inductively coupled flux qubits
• Analysis of a tuneable coupler for superconducting phase qubits
• Quantum crossover in moderately damped epitaxial NbN/MgO/NbN junctions with low critical current density
• Coherent dynamics and decoherence in a superconducting weak link
• Probing High Frequency Noise with Macroscopic Resonant Tunneling
• Observation of Co-tunneling in Pairs of Coupled Flux Qubits
• Microstrip filters for measurement and control of superconducting qubits
• Non-Markovian incoherent quantum dynamics of a two-state system
• A tunable rf SQUID manipulated as flux and phase qubit
• Detector of microwave photon pairs based on a Josephson photomultiplier
• Two-photon coupling via Josephson element I: Breaking the symmetry with magnetic fields
• Tunneling without tunneling: wavefunction reduction in a mesoscopic qubit