Quantum amplifier plays a key role in superconducting quantum computers for multiplexed single-shot qubit readout. In order to realize a home-made quantum computer on the road, we must build this technology by our own. Here we propose an integrated project aiming to develop superconducting parametric amplifiers (PAs) to support scalable superconducting quantum computer developments in Taiwan. The proposal is comprised of three subprojects. The first and second subproject are focused on developing traveling wave parametric amplifier (TWPA), by using different approaches to enhance the nonlinearlity of Josephson junctions (JJs). In the first subproject TWPA is consisted of series-connected Nb-JJs embedded in the transmission lines, and the second one will utilize non-linear kinetic inductance of ultrathin NbTiN superconducting transmission lines. TWPA require a larger pump power, and can have a relatively wider bandwidth and a larger dynamic range, the characteristics necessary for superconducting qubit readout multiplexing. The third subproject concentrates on Al-based Josephson parametric amplifiers (JPAs), including both negative resistance reflection and traveling-wave types. Aluminum is rather popular for constructing JPAs due to its oxide properties and fabrication convenience. We plan to adopt three major JPA designs: flux-driven JPA, lumped-element JPA, and traveling-wave JPA, ranging from simple to complex. Narrowband flux-driven JPAs are used to study standard operation procedures of amplifiers to establish characterization routines for screening devices and accumulate device performance statistics. Wideband lumped-element JPAs will be the major product. Traveling-wave JPAs with even wider bandwidth and higher saturation power will be developed for future expansions.  Our goal is to produce wafer-scale, high-yield, wideband, quantum-limited PAs. To achieve the goal, we unfold the project into 5-year tasks. We set target specifications of each type of PAs to meet the needs of superconducting qubit operations. We present the preliminary data testing in the prototype devices to show our current status, describe collaboration details and schedule assignments in each team. The outcomes of the project will not only strengthen the developments of scalable superconducting quantum computers, but also boost quantum controls and precision measurements in microwave regimes.

     The fourth subproject is parametric-amplifier-assisted spin qubit readout. The physical mechanism for spin qubit readout is the quantum capacitance originating from the single charge tunneling in quantum dot arrays. This quantum capacitance shifts the resonance frequency of the readout resonator, which changes the phase of the reflect microwave signal. We aim to enhance the spin readout fidelity using the parametric amplifiers developed in this project.