Flux-Pumped Josephson Traveling-Wave Parametric Amplifier with Reverse Isolation

Traveling-wave parametric amplifiers (TWPAs) have emerged as one of the leading technologies to amplify signals coming from frequency-multiplexed readout resonators. As such, they are a cornerstone in scaling up the readout architecture of superconducting quantum computers.

In principle, an ideal TWPA has a unity reverse gain, and therefore strong isolation should only be necessary after the TWPA to protect the device under test (DUT) from extraneous noise. However, in practice, unavoidable signal and pump reflections leads to a finite amount of reverse gain. As a consequence, isolation between the TWPA and the DUT is required. In addition, the co-propagating pump is often delivered via a directional coupler, also placed between the DUT and the TWPA. These additional components limit the scalability and noise performance of the amplification chain.

In this talk, we will present a new type of TWPA which intends to mitigate spurious backaction by combining flux pumping and reverse isolation. This TWPA could be connected directly to the DUT, without intermediate isolator or directional coupler, leading to a highly efficient and scalable microwave readout chain.