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Phase Locking Transition in a Chirped Superconducting Josephson Resonator



Jose A. Aumentado, Ofer Naaman, L Friedland, J.S. Wurtele, Irfan Siddiqi


We observe a sharp threshold for autoresonant phase locking in a transmission line resonator embedded with a Josephson tunnel junction and driven with a purely ac, chirped microwave signal. When the drive amplitude is below a critical value, the resonator is only slightly excited when the drive frequency is commensurate with the linear resonance frequency. For a larger amplitude, the resonator phase-locks to the chirped drive and its amplitude grows until a deterministic maximum is reached. The system evolves smoothly to one basin of attraction or another without switching, depending on the drive amplitude and chirp rate. The critical drive amplitude depends strongly on the junction critical current, thus forming a new type of Josephson amplifier: the Josephson autoresonant amplifier (JARA). The observed critical behavior agrees well with theory and suggests a new modality for quantum state measurement.
Nature Physics


superconductivity, quantum measurement, josephson junctions, amplification, quantum computing


Aumentado, J. , Naaman, O. , Friedland, L. , Wurtele, J. and Siddiqi, I. (2008), Phase Locking Transition in a Chirped Superconducting Josephson Resonator, Nature Physics, [online], (Accessed April 18, 2024)
Created September 12, 2008, Updated February 19, 2017