Experimental characterization of RF-SQUIDs based Josephson Traveling Wave Parametric Amplifier exploiting Resonant Phase Matching scheme

In this contribution, we will present recent advances on Josephson Traveling Wave Parametric Amplifiers (JTWPAs) developed and tested at the Italian National Research Institute of Metrology (INRiM). JTWPAs are engineered micro-structured metamaterials composed of a repetition of several hundreds of Josephson junctions embedded in a superconducting coplanar waveguide. The Josephson junctions confer to the material a non-linear behavior and promote a medium-mediated energy exchange, known as parametric down-conversion, between a strong propagating microwave tone and a couple of energy-preserving weak tones, called respectively signal and idler. This working principle makes the JTWPAs both an important tool for quantum limited broadband microwave amplification (i.e., with the smallest added noise allowed by the uncertainty principle) and for the emission of non-classical microwave radiation, being the signal and idler tones composed by entangled photons, exploitable in a wide variety of quantum sensing techniques such as quantum illumination, and quantum key distribution or for absolute calibration of microwave single photon detectors. In particular, we will present experimental characterization of an Al/Al-Ox/Al rf-SQUIDs-based JTWPA equipped with a resonant phase matching scheme [8], designed using finite element electromagnetic simulations in order to mitigate some typical unwanted effects like energy dissipation in higher-harmonics, internal reflections due to impedance mismatch and generation of slot line modes. The performance of this device, measured in a properly equipped dilution refrigerator (T<50mK), will be quantified in terms of classical quantities like gain, bandwidth, and saturation power, while the signature of the emission of non-classical radiation will be detected employing IQ voltage quadratures correlation measurements.