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 L∼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.
@article{arxiv.1404.1792,
title = {Tunable microwave impedance matching to a high impedance source using a Josephson metamaterial},
author = {Carles Altimiras and Olivier Parlavecchio and Philippe Joyez and Denis Vion and Patrice Roche and Daniel Esteve and Fabien Portier},
journal= {arXiv preprint arXiv:1404.1792},
year = {2014}
}