Lumped-element broadband SNAIL parametric amplifier with on-chip pump filter for multiplexed readout

TL;DR

This paper introduces a compact, robust SNAIL-based broadband parametric amplifier with integrated on-chip pump filtering, achieving high gain, low distortion, and effective multiplexed qubit readout for quantum computing applications.

Contribution

It presents a novel lumped-element impedance matching network and on-chip pump filter integrated into a SNAIL amplifier, fabricated with simple lithography, enabling high performance and scalability.

Findings

20 dB gain with <1 dB ripple over 250 MHz bandwidth

Intermodulation products suppressed by >23 dB at 1 dB gain compression

Achieved high-fidelity readout of two qubits with over 98% fidelity

Abstract

We present a SNAIL-based parametric amplifier that integrates a lumped-element impedance matching network for increased bandwidth and an on-chip pump-port filter for efficient pump delivery. The amplifier is fabricated using a single-layer optical lithography step, followed by a single-layer electron beam lithography step. We measure a flat 20 dB gain profile with less than 1 dB ripple across a bandwidth of up to 250 MHz on multiple devices, demonstrating robust performance against variations arising from fabrication and packaging. We characterize the amplifier's linearity by analyzing gain compression and intermodulation distortion under simultaneous multi-tone excitation. We show that the intermodulation products remain suppressed by more than 23 dB relative to the signal tones, even at the 1 dB gain compression point. We further validate its utility by performing simultaneous high-fidelity readout of two transmon qubits, achieving state assignment fidelities of 99.51% and 98.55%. The combination of compact design, fabrication simplicity, and performance robustness makes this amplifier a practical device for quantum experiments with superconducting circuits.