Tunable microwave impedance matching to a high impedance source using a Josephson metamaterial

  1. Carles Altimiras,
  2. Olivier Parlavecchio,
  3. Philippe Joyez,
  4. Denis Vion,
  5. Patrice Roche,
  6. Daniel Esteve,
  7. and Fabien Portier
We report the efficient coupling of a 50Ω microwave circuit to a high impedance conductor. We use an impedance transformer consisting of a λ/4 co-planar resonator whose inner conductor contains an array of superconducting quantum interference devices (SQUIDs), providing the resonator with a large and tunable lineic inductance ∼80μ0, resulting in a large characteristic impedance ZC∼1kΩ. The impedance matching efficiency is characterized by measuring the shot noise power emitted by a dc biased high resistance tunnel junction connected to the resonator. We demonstrate matching to impedances in the 15 to 35kΩ range with bandwidths above 100MHz around a resonant frequency tunable in the 4 to 6GHz range.
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