A Traveling Wave Parametric Amplifier Isolator

  1. Arpit Ranadive,
  2. Bekim Fazliji,
  3. Gwenael Le Gal,
  4. Giulio Cappelli,
  5. Guilliam Butseraen,
  6. Edgar Bonet,
  7. Eric Eyraud,
  8. Sina Böhling,
  9. Luca Planat,
  10. A. Metelmann,
  11. and Nicolas Roch
Superconducting traveling-wave parametric amplifiers have emerged as highly promising devices for near-quantum-limited broadband amplification of microwave signals and are essential for high quantum-efficiency microwave readout lines. Built-in isolation, as well as gain, would address their primary limitation: lack of true directionality due to potential backward travel of electromagnetic radiation to their input port. Here, we demonstrate a Josephson-junction-based traveling-wave parametric amplifier isolator. It utilizes third-order nonlinearity for amplification and second-order nonlinearity for frequency upconversion of backward propagating modes to provide reverse isolation. These parametric processes, enhanced by a novel phase matching mechanism, exhibit gain of up to 20~dB and reverse isolation of up to 30~dB over a static 3~dB bandwidth greater than 500~MHz, while keeping near-quantum limited added noise. This demonstration of a broadband truly directional amplifier ultimately paves the way towards broadband quantum-limited microwave amplification lines without bulky magnetic isolators and with inhibited back-action.
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