Gain and noise performances of TWPAs are severely limited in scientifically and technologically interesting conditions, such as in magnetic elds and in high power regimes. TruePA aims to overcome this limitation by employing a strategy based on disordered, high kinetic inductance materials and by the design of proper magnetic shielding. So far we could verify a record tunability as well as strong resilience against in-plane magnetic fields for our material of choice which is based on granular aluminium films. Hence, in combination with novel designs to reduce the dissipation from mobile vortices/uxons, we are on the pathway to achieve our first goal of truly field-resilient TWPAs.
Regarding our second objective to develop truly quantum limited TWPAs we have made progress on the theoretical and experimental side. We have analysed the impact of fabrication imperfections and developed new hardware design to reduce losses and impedance matching. TruePA partner PTB achieved and verified near quantum-limited performance of an RF-SQUID-based JTWPA. Moreover, we performed a detailed experimental study of pump harmonics augmented with numerical simulations, enabling us to characterize, understand and mitigate spurious wave-mixing processes. Overall, we were able to reduce losses by optimizing fabrication processes and materials, as well as reduce noise contributions due to high-pump-powers, and see TruePA on track for achieving our goal of truly quantum-limited TWPAs.
We have achieved our goal to develop a truly nonreciprocal TWPA based on a two-pump protocol, where one pump mediates the amplification process and the other depletes the signal channel via a frequency conversion process. The so-called TWPAI has remarkable features, it exhibits fully directional gain of up to 20 dB and reverse isolation of up to 30 dB, resulting in a directionality of about 50 dB over a static 3-dB-bandwidth larger than 500 MHz.
