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Guilliam Butseraen presents

  Graphene-based superconducting quantum circuits: the Josephson parametric amplifier

Tuesday, November 8th 2022 at 9:30 am

Seminar room – Building A – CNRS

The defence will be in French.



With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited parametric amplifiers have proven to be essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of µeV). They are also used to generate non classical states of light that can be a resource for quantum enhanced detection. Superconducting parametric amplifiers, like quantum bits, typically utilise a Josephson junction as a source of magnetically tunable and dissipation-free nonlinearity. The magnetic control is not an industry standard for devices and starts already to be an issue in large scale circuits. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable nonlinear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and graphene. However, given the challenge of balancing nonlinearity, dissipation, participation, and energy scale, parametric amplifiers have not yet been implemented with a semiconductor weak link. In this presentation, I will demonstrate the design, fabrication and performances of a gate tunable parametric amplifier leveraging a graphene Josephson junction. More particularly, I will show that such an amplifier can have gains exceeding 20 dB. Thanks to the field effect, we can tune this gain over a 1GHz frequency range by applying a gate voltage on the graphene junction. The 1dB compression point can reach up to -123 dBm and the amplifier exhibits added noise close to the standard quantum limit.