Periodic Reporting for period 1 - TruePA (Truly Resilient Quantum Limited Traveling Wave Parametric Amplifiers)
Reporting period: 2022-12-01 to 2024-05-31
TruePA will develop the next generation of Traveling Wave Parametric Amplifiers (TWPAs), which are key tools for quantum technologies and basic sciences involving the detection of weak electromagnetic signals in the microwave domain. TruePA aims at pushing TWPA devices beyond current limits pursuing three main ground-breaking advances: demonstration of TWPAs which are (i) resilient to magnetic fields, (ii) quantum-noise-limited and (iii) fully nonreciprocal. Our approach integrates novel circuit designs and the use of advanced superconducting materials, combined with new characterization methods based on quantum optics techniques. The outcomes of TruePA will highly advance the field of quantum-limited amplifiers providing novel insights into decoherence mechanisms in superconducting circuits and boosting microwave amplification performance in basic science research fields such as quantum information with solid state platforms, astronomy and dark matter search. TruePA brings together internationally known researchers with complementary expertise in the field of superconducting circuits, quantum amplifiers, nanofabrication and quantum optics. This specialized knowledge is complemented by the expertise of two industry partners, to push a new generation of TWPAs to off-the-shelf components contributing to the growth of quantum technologies in Europe and at the same time pushing forward basic science research.
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.
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.
The TruePA project aims at improving traveling-wave parametric amplifiers by developing original architectures and pushing the current theoretical understanding of their physics. The end goal is to better understand traveling-wave parametric amplification and to make TWPAs even more beneficial for end users. One of our first results is the demonstration of magnetic-field resilience of disordered superconducting materials. This is a crucial step towards field-resilient TWPAs, as the current generation of superconducting parametric amplifiers are very sensitive to magnetic fields, and magnetic shielding is required to reduce the negative impact on the gain and noise performance. The magnetic field sensitivity also limits the usage of these devices in applications where an applied magnetic field is an integral part of the experimental setup such as Electron Spin Resonance experiments or superconducting detectors cooled in Adiabatic Demagnetisation (ADR) cryostats. Moreover, a flaw in current TWPAs is their inability to reach the actual quantum limit of noise. The TruePA project aims to understand the relevant noise sources and develops strategies to mitigate them. Here an important result is our thorough experimental and theoretical study of spurious wave-mixing processes, as well as the developments of new fabrication techniques which reduces the noise contributions. A key result of our project is the demonstration of a truly nonreciprocal TWPA. A result going beyond the state of the art as current TWPAs are almost completely reciprocal: a signal can travel in both directions. This feature is challenging for an experimental setup, as it allows perturbations and noise to perturb devices under test, which are generally very sensitive. Our nonreciprocal TWPA is a great leap forward for current microwave setups in cryogenic environment. It could supplant the best readout fidelities that are achieved today, while leading to a much more scalable solution for readout lines in current experimental setup.