The paper investigates the interplay of nonlinear effects with the non-ideal transmission properties of a Josephson Travelling Wave Parametric Amplifier (JTWPA). Experimental characterization using a microwave and DC cryogenic setup reveals periodic transmission modulation linked to the tuning of the Josephson inductances embedded in the line. The effects of impedance matching and resonant parametric down-conversion (PDC) are observed on a broadband scale, and the impact of design parameters and fabrication issues on device performance is analyzed. These findings contribute to the optimizing techniques for JTWPA devices, advancing quantum-limited amplifiers.
The paper investigates the interplay of nonlinear effects with the non-ideal transmission properties of a Josephson Travelling Wave Parametric Amplifier (JTWPA). Experimental characterization using a microwave and DC cryogenic setup reveals periodic transmission modulation linked to the tuning of the Josephson inductances embedded in the line. The effects of impedance matching and resonant parametric down-conversion (PDC) are observed on a broadband scale, and the impact of design parameters and fabrication issues on device performance is analyzed. These findings contribute to the optimizing techniques for JTWPA devices, advancing quantum-limited amplifiers.
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.
A comprehensive numerical analysis of the dynamical response of Josephson Traveling Wave Parametric Amplifiers (JTWPA) under varying driving conditions is presented. The primary goal is to examine the effects of a current–phase relation (CPR) incorporating a second-harmonic contribution. The analysis further investigates how parameters such as pump intensity, signal frequency, and DC bias current influence the transition to chaos. The results reveal a wide range of dynamical regimes in JTWPAs, offering insights into optimizing device performance and stability. Notably, the shape of the CPR is shown to have a significant impact on the operational effectiveness and stability of JTWPAs. To obtain results closer to real devices, numerical modeling of JTWPAs implementing Resonant Phase Matching (RPM) circuitry has been performed. We have verified that the introduction of RPM allows a significant increase in the amplifier gain also in the case of non-sinusoidal CPR. These findings may have important implications for the development of next-generation JTWPAs, which are essential components in quantum computing and precision measurement applications.
This work presents the design, fabrication strategy, and numerical modeling of niobium-based Josephson traveling-wave parametric amplifiers (JTWPAs) for quantum microwave readout. These devices are designed as nonlinear transmission lines composed of more than two thousand Josephson junction unit cells, with periodically embedded resonators enabling phase matching. The use of Nb trilayer technology (Nb/AlO[Formula: see text]/Nb) with respect to Al-based devices ensures higher junction uniformity, lower losses, and higher resilience to stray magnetic fields. We developed a multi-scale modeling framework combining harmonic balance methods and time-domain simulations of nonlinear coupled differential equations to describe wave propagation, parametric amplification, and spectral dynamics. Numerical results predict broadband gain up to 20[Formula: see text]dB over multi-GHz bandwidths. These results demonstrate the potential of Nb-based JTWPAs as scalable components for quantum applications.
A major challenge for the experimental realization of advanced superconducting traveling-wave parametric amplifiers is given by proper impedance matching of the input and output transmission lines and the active region with periodically embedded Josephson junction arrays. For a large impedance mismatch, non-negligible reflections occur at the interfaces, leading to a co-propagation of cavity-like modes. In this contribution, we want to assess the effects of improper impedance matching on the transmission spectrum of traveling-wave parametric amplifiers using a simple overlay cavity model. Our results can serve as a guideline for design limitations of Josephson-junction-embedded transmission lines.
Recent progress in physics has increased the necessity for ultra-low noise amplifiers capable of operating at the quantum limit performance. These amplifiers are essential to enhance astronomical detection, dark-matter search, and qubit readout in quantum computing, among other applications. Superconducting Josephson junction Travelling Wave Parametric Amplifiers (JTWPAs) operated in the microwave range, have demonstrated high gain over several gigahertz (GHz) bandwidth, with quantum-limited noise performance and minimal heat dissipation. These excellent properties make JTWPAs an ideal solution for ultra-low noise amplification. This thesis delves into the design, fabrication and characterisation of JTWPAs operated in the microwave (1-16 GHz) and the W-band (70-115GHz) regimes. A generalised coupled-mode equations (CME) framework describing JTWPAs based on Josephson junctions and DC superconducting quantum interference devices (SQUIDs) is introduced. This framework can be combined with electromagnetic (EM) simulation softwares to model the JTWPAs, facilitating their design. It is therefore used to model two microwave JTWPA designs, using parallel plate capacitors (PPCs) and interdigitated capacitors (IDCs). The fabrication and characterisation of both designs are presented, and possible fabrication and design issues are carefully discussed. Despite these issues, we observed broadband gain in the JTWPA with PPCs, achieving > 20 dB gain at several frequency points, and a measured P1dB = −95.8dBm when operated at 17.3 dB. The RF properties of a 500-junction Josephson array are also presented in this manuscript. The device creates a Fabry-Perot cavity, leading to non-travelling wave parametric effects, such as narrow-band gain. We also observed indications of efficient phase-sensitive amplification. The thesis is concluded with the first — to the best of our knowledge — experimental attempt to extend the operational frequency of a JTWPA to the W-band. The novel design, fabrication techniques and characterisation of the W-band JTWPA are discussed in detail in this manuscript, leading to promising results suggesting that JTWPA could operate at high frequencies.
In this work, we develop a comprehensive numerical analysis of the dynamic response of a Josephson Traveling Wave Parametric Amplifier (JTWPA) by varying the driving parameters, with a focus on the pathways leading to chaotic behavior. By tuning the working conditions, we capture the broad spectrum of dynamical regimes accessible to JTWPAs, delineating the settings under which transition to chaos occurs. Furthermore, we extend our investigation to device formed by junctions characterized by a non--sinusoidal current phase relation (CPR) and exploring the impact of its shape on the amplifier's performance. Through the study of gain characteristics, Poincaré sections, and Fourier spectra, we provide an in-depth understanding of how non-linearity and CPR nonsinusoidality influence the JTWPAs' operational effectiveness and stability. This investigation offers insights into optimizing the device designs for enhanced performance and robustness against chaotic disruptions, in order to establish a framework for predicting and controlling JTWPA behavior in practical applications. This effort will pave the way for the development of devices with tailored dynamic responses and for advancements in quantum computing and precision measurement technologies, where stability and high fidelity are of paramount importance.