Dr. Boon Kok Tan

Abstract:

Most Josephson junction Travelling Wave Parametric Amplifiers (JTWPAs) developed so far have been focused on operation below 20 GHz, primarily driven by the choice of the qubit resonance frequency used in quantum computation research. Consequently, there is a lack of effort to extend their operation to higher frequency ranges. However, millimetre (mm)- wave JTWPAs could offer potential significant advantages for astronomy, but their operation in this regime is largely unexplored. In this paper, we describe the design considerations for extending JTWPAs operation to the W-band range. We present two JTWPA designs, one with and one without phase matching elements, and we discuss the design methodology of both approaches, before showing their predicted performance respectively.

Abstract:

Josephson-junction-based parametric amplifiers (JPAs) are key enabling technologies in superconducting quantum electronics, supporting applications ranging from dark-matter detection to quantum-computing readout. However, conventional JPAs are intrinsically narrowband, motivating the development of broadband architectures such as impedance-matched parametric amplifiers (IMPAs), which enhance bandwidth through the incorporation of auxiliary passive resonators.

In this work, we present the design and fabrication of a three-pole kinetic-inductance impedance-matched parametric amplifier (KIMPA) based on a niobium titanium nitride (NbTiN) nonlinear nanowire and implemented using an inverted microstrip architecture. The amplifier is synthesised using the multipole filter-design framework of Naaman and Aumentado and targets a 10% fractional bandwidth centred at 6 GHz with 20 dB gain. The device employs a multilayer architecture consisting of a 30 nm NbTiN wiring layer, a 150 nm amorphoussilicon dielectric layer, and a 200 nm niobium sky plane, enabling compact parallel-plate capacitors and improved fabrication robustness compared with conventional coplanar-waveguide implementations.

The design methodology is presented from the graph-based filter-synthesis model through circuit-level implementation and physical layout generation. Harmonic-balance simulations predict approximately 20 dB gain across a 6.0–6.4 GHz operating band, demonstrating the feasibility of broadband kinetic-inductance parametric amplification in an inverted microstrip platform. Fabricated devices have been completed and are currently being prepared for cryogenic characterisation.

Abstract:

Kinetic inductance travelling-wave parametric amplifiers (KITWPAs) have emerged as promising quantum-limited amplifiers for large-format detector arrays and quantum sensing applications. Extending this technology to millimetre-wave frequencies could enable ultra-low-noise pre-amplification for astronomical heterodyne receivers, potentially improving receiver sensitivity and mapping speed. In this work, we present the preliminary design of a W-band three-wave mixing (3WM) KITWPA based on a high-kinetic-inductance niobium-titaniumnitride (NbTiN) inverted microstrip transmission line.

The proposed architecture incorporates waveguide-coupled radial-probe transitions and a DC-bias network adapted from established superconducting mixer technologies to enable 3WM operation at millimetre-wave frequencies. Electromagnetic simulations are combined with coupled-mode analysis to evaluate the amplifier performance. Simulations predict an intrinsic gain exceeding 20 dB over a broad frequency range from 30 to 110 GHz. When integrated within a WR-10 waveguide environment, the effective operating bandwidth is predicted to extend from 75 to 110 GHz with more than 15 dB gain. The proposed design demonstrates the feasibility of implementing DC-biased 3WM KITWPAs in the W-band and represents a potential route towards low-noise pre-amplifiers for future mm-wave and submm-wave heterodyne receiver systems.