This study presents recent advancements in Josephson Traveling Wave Parametric Amplifiers (JTWPAs) developed and tested at INRiM within the DARTWARS project framework. Combining Josephson junctions with superconducting coplanar waveguides, JTWPAs offer advanced capabilities for quantum-limited broadband microwave amplification and the emission of non-classical microwave radiation. The work delves into the architecture, optimization, and experimental characterization of a JTWPA with a Resonant Phase-Matching mechanism, highlighting signal gains and idler conversion factors in relation to pump power and signal frequency.
Josephson traveling-wave parametric amplifiers (JTWPAs) are key to fast, frequency-multiplexed measurements in superconducting circuits. JTWPAs with periodic modulation are attractive, as they phase match without flux or dc bias, but they often suffer from significant gain ripples. Another common limitation in JTWPAs is intrinsic loss, which has prevented them from reaching the quantum limit of added noise. Here researchers address both issues by implementing an all-aluminum coplanar lumped-element JTWPA, using a qubit-compatible fabrication recipe. Their modulated device suppresses gain ripples for smooth, bias-free amplification, and approaches the quantum limit of added noise.
Traveling wave parametric amplifiers (TWPAs) with added noise approaching the quantum limit have enabled highly sensitive microwave frontends for qubit readout, radio astronomy, and particle physics. These amplifiers operate by mixing a strong microwave pump wave with the signal in a nonlinear waveguide, in such a way that a fraction of the pump power is used to amplify the signal and generate a co-propagating idler wave. Conventional TWPAs rely on the inductive nonlinearity originating from the Josephson effect or kinetic inductance in thin super-conductors, restricting these devices to use cases below 4K and nonmagnetic environments. In this work, we propose a C-band TWPA where a capacitive nonlinearity is engineered in transmission lines based on the paraelectric material
SrTiO3. The nonlinear properties of
SrTiO3remain stable at much higher temperatures (20K) and in high magnetic fields. We have developed a theoretical framework for the optimal geometry of
SrTiO3-based nonlinear transmission lines to achieve phase-matched parametric processes while minimizing the required pump power. Periodically loaded coplanar-waveguide (CPW)-like structures on thin-film
SrTiO3are simulated to have 20dB of gain over 100mm of interaction, based on empirical nonlinear models of
SrTiO3. Alternative methods including slotline geometries and bulk
SrTiO3are also simulated. Preliminary measurements of thin-film
SrTiO3properties and amplifiers are presented as well as plans to fabricate devices that operate near 500MHz for the Project-8 neutrino mass experiment.