Javier Navarro

Abstract:

Superconducting Parametric Amplifiers (SPAs) with near-quantum-limited added noise are crucial for weak signal detection applications such as astronomical receivers, quantum computation, and fundamental physics experiments. Commercially available SPAs include Josephson Parametric Amplifiers (JPAs), which offer high gain but narrow bandwidth performance; and Josephson-junction Travelling Wave Parametric Amplifiers (JTWPAs), which provide broader bandwidth at the cost of a complicated fabrication procedure, lower fabrication yield, and larger footprint area. In this paper, we investigate the parametric amplification of microwave signals in a Josephson array embedded in a low-Q Fabry-Pérot cavity. We fabricated a 500-junction array device and measured >15 dB phase-preserving gain over a ∼350 MHz bandwidth, while offering almost two orders of magnitude improvement in compression point (P1dB = −106.2 dBm) compared to standard JPAs. Furthermore, using a novel measurement technique, we configured our device to operate in the phase-sensitive mode, measuring a phase-sensitive extinction ratio (PSER) of 42.3 ± 2.81 dB, in line with state-of-the-art values for JPAs. These promising performances, combined with the ease of fabrication and improved yield compared with JTWPAs, underscore the potential of these devices for applications in advanced detection schemes.

Abstract:

Superconducting travelling-wave parametric amplifiers (TWPAs) play a vital role in a range of high-sensitivity applications. These devices can be realised using various superconducting materials, such as high kinetic inductance films or low-loss transmission lines embedded with discrete nonlinear elements like Josephson junctions (JJs) or superconducting quantum interference devices (SQUIDs), and can operate across different wave-mixing regimes. However, a unifying framework for quick assessment and thus efficiently evaluating the performance of these diverse TWPA architectures, particularly during the design phase, remains lacking. Most existing models are derived from first principles for specific TWPA designs and lack general applicability. While certain simulation program with integrated circuit emphasis (SPICE) tools can more accurately emulate TWPA behaviour post-design, they are typically computationally intensive, time-consuming, and offer limited physical insight; especially regarding key performance-determining factors such as phase matching. This, in turn, impedes the rapid identification of optimal TWPA configurations. In this work, we extend a previously introduced framework for kinetic-inductance (KI-) TWPAs and demonstrate its applicability to a broader class of χ(3)-type TWPA configurations, including bare JJ (JTWPA) and symmetric SQUID-based TWPAs, operating in all wave-mixing modes. This approach facilitates rapid design-space exploration prior to detailed optimisation using SPICE-based simulations. Our method accommodates a wide range of unit cell topologies and meta-material parameters without requiring ground-up derivations from first principles. We validate the framework by comparing it against representative models from the literature, including JJ-, KI-, and DC SQUID-based TWPA designs, and show that it reliably captures the first-order behaviour of their gain–bandwidth characteristics.

Abstract:

The development of superconducting travelling-wave parametric amplifiers (TWPAs) over the past decade has highlighted their potential as low-noise amplifiers for use in fundamental physics experiments and industrial applications. However, practical challenges, including signal-idler contamination, complex pump injection and cancellation, impedance mismatch, and the reciprocal nature of the device, have made it challenging to deploy TWPAs in real-world applications. In this paper, we introduce an innovative solution to these issues through phase-controlled balanced-TWPA architectures. These architectures involve placing two TWPAs in parallel between a pair of broadband couplers. By carefully controlling the phases of the tones propagating along the TWPAs, we can effectively separate the signal and idler tones, as well as the pump(s), using a straightforward injection and cancellation mechanism. The balanced-TWPA architecture offers versatility and flexibility, as it can be reconfigured either intrinsically or externally to suit different application needs. In this manuscript, we provide a comprehensive discussion of the working principles of the balanced-TWPA, including various configurations designed to meet diverse application requirements. We also present the expected gain-bandwidth products in comparison to traditional TWPAs and conduct tolerance analysis to demonstrate the feasibility and advantages of the balanced-TWPA architecture. By addressing the practical challenges associated with TWPAs, the balanced-TWPA architecture represents a promising advancement in the field, offering a more practical and adaptable solution for a wide range of applications.

Abstract:

Travelling Wave Parametric Amplifiers (TWPAs) can potentially achieve quantum limited noise over a broad bandwidth in the microwave regime, with potential applications in the readout of millimetre (mm) and sub-millimetre (sub-mm) receivers to further improve the system sensitivity, among many other applications. TWPAs using embedded Josephson junctions (J-TWPA) have proven to exhibit noise performance approaching the quantum limit, however its compression point (P_–1dB ~ –100 dBm) is too low for reading out mm and sub-mm astronomical receivers. Therefore, we explored the design of higher dynamic range JTWPAs to match the power requirements, and to optimise the performances of the JTWPA for this specific application. Our aim is to adapt the well-established Nb-AlO_x-Nb tri-layer fabrication technique used routinely for developing high-quality Superconductor-Insulator-Superconductor (SIS) tunnel junctions to fabricate our JTWPA. Therefore, we present in this paper our investigation of the feasibility of such technique in fabricating large number of lower critical current density junctions embedded in a coplanar waveguide (CPW). The preliminary results on a 500-junctions device are in line with the expected behaviour, showing a measured gain consistent with theoretical calculations which demonstrates the potential use of the tri-layer tunnel junction technology for the fabrication of JTWPAs.