Microwave irradiation and quasiparticles in a superconducting double dot

John Nicholas Lambert, A. A. Esmail, F. A. Pollock, M. Edwards, B. W. Lovett, A. J. Ferguson

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We study the interaction of the charge states of a superconducting double dot, comprising two superconducting islands coupled by a Josephson junction, with microwaves between 2 and 55 GHz. We observe resonant transitions between even-parity charge states at relatively low frequencies and breaking of Cooper pairs under higher-frequency irradiation, allowing our device to act as a click detector for microwave photons. By applying a magnetic field and tuning the pair-breaking energy, we perform spectroscopy on the environment in our cryostat and determine the temperature of a nonequilibrium photon bath. Finally, we exploit the band structure of our device to break Cooper pairs dependent on the symmetry of the initial Cooper pair state.

Original languageEnglish
Article number235413
Number of pages10
JournalPhysical Review B
Issue number23
Publication statusPublished - 9 Jun 2017

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