# Broadband lumped-element Josephson parametric amplifier with single-step lithography

## TL;DR

This paper introduces a simple, single-step lithography process for fabricating a Josephson parametric amplifier with high gain, broad bandwidth, and tunability, suitable for quantum information applications.

## Contribution

The work demonstrates a straightforward fabrication method for JPAs using single electron beam lithography and shadow evaporation, enabling reliable large junctions and tunable performance.

## Key findings

- Achieved 20 dB gain with 95 MHz bandwidth at 5 GHz
- Center frequency tunable by over 1 GHz and rapidly via pump frequency
- Analytical models closely match experimental results

## Abstract

We present a lumped-element Josephson parametric amplifier (JPA) utilizing a straightforward fabrication process involving a single electron beam lithography step followed by double-angle evaporation of aluminum and in-situ oxidation. The Josephson junctions forming the SQUID are fabricated using bridgeless shadow evaporation technique, which enables reliable fabrication of relatively large ($\sim9~\mathrm{\mu m^2}$) junctions. Our strongly coupled flux-pumped JPA achieves 20~dB gain with 95~MHz bandwidth around 5~GHz, while the center frequency is tunable by more than 1~GHz, with the additional possibility for rapid tuning by varying the pump frequency alone. Analytical calculations based on the input-output theory reproduce our measurement results closely.