Non-degenerate parametric amplifiers based on dispersion engineered Josephson junction arrays

TL;DR

This paper introduces a dispersion engineered Josephson junction array-based non-degenerate parametric amplifier capable of high-fidelity, continuous quantum jump detection in transmon qubits within the 1-10 GHz range, fabricated with standard lithography.

Contribution

It presents a novel, fabrication-friendly parametric amplifier design using JJ arrays with flux tunability, enabling broad frequency coverage for quantum measurements.

Findings

Achieved 90% fidelity in quantum jump detection.

Demonstrated amplification at multiple eigenmodes below 10 GHz.

Potential for covering the entire 1-10 GHz frequency band.

Abstract

Determining the state of a qubit on a timescale much shorter than its relaxation time is an essential requirement for quantum information processing. With the aid of a new type of non-degenerate parametric amplifier, we demonstrate the continuous detection of quantum jumps of a transmon qubit with 90% fidelity in state discrimination. Entirely fabricated with standard two-step optical lithography techniques, this type of parametric amplifier consists of a dispersion engineered Josephson junction (JJ) array. By using long arrays, containing $10^3$ JJs, we can obtain amplification at multiple eigenmodes with frequencies below $10~\mathrm{GHz}$, which is the typical range for qubit readout. Moreover, by introducing a moderate flux tunability of each mode, employing superconducting quantum interference device (SQUID) junctions, a single amplifier device could potentially cover the entire frequency band between 1 and $10~\mathrm{GHz}$.