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arXiv:2505.02740 · Physical Review Applied

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

Vidul Joshi, Sumeru Hazra, Andy Z. Ding, Alessandro Miano, Wei Dai, Gautham Umasankar, Akshay Koottandavida, G. Liu, Luigi Frunzio, Michel Devoret

Published Aug 27, 2025• 3 citations

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.

DOI: 10.1103/5l86-pw21

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Broadband impedance-matched Josephson parametric amplifiers are key components for high-fidelity single-shot multi-qubit readout. Nowadays, several types of impedance matched parametric amplifiers have been proposed: the first is an impedance-matched parametric amplifier based on a Klopfenstein taper, and the second is the impedance-matched parametric amplifier based on auxiliary resonators. Here, we present the quantum-limited 3-wave-mixing lumped-element SNAIL parametric amplifier with two-pole impedance matching transformer. A two-pole Chebyshev matching network with shunted resonators is based on parallel-plate capacitors and superconducting planar coil. Operating in a flux-pumped mode, we experimentally demonstrate an average gain of 15 dB across a 600 MHz bandwidth, along with an average saturation power of −107 dBm and quantum-limited noise temperature.

Broadband impedance-matched Josephson parametric amplifiers are key components for high-fidelity single-shot multi-qubit readout. Nowadays, several types of impedance matched parametric amplifiers have been proposed: the first is an impedance-matched parametric amplifier based on a Klopfenstein taper, and the second is an impedance-matched parametric amplifier based on auxiliary resonators. Here, we present the quantum-limited 3-wave-mixing lumped-element SNAIL parametric amplifier with two-units impedance matching transformer. A two-pole Chebyshev matching network with shunted resonators based on parallel-plate capacitors and superconducting planar coil. Operating in a flux-pumped mode, we experimentally demonstrate an average gain of

15dB

across a

600MHz

bandwidth, along with an average saturation power of

-107dBm

and quantum-limited noise temperature.

Broadband quantum-limited amplifiers play a critical role in the single-shot readout of superconducting qubits, but a popular implementation, the traveling wave parametric amplifier, involves a complex design and fabrication process. Here, we present a simple design for a Josephson parametric amplifier, using a lumped element resonator comprising a superconducting quantum interference device whose useful bandwidth is enhanced with an on-chip impedance-matching circuit. We demonstrate a flux-coupling geometry that maximizes the coupling to the Josephson loop and minimizes spurious excitation of the amplifier resonant circuit. The amplifier, which operates in a flux-pumped mode, is demonstrated with a power gain of more than 20 dB over a bandwidth of about 300 MHz, where approximate noise measurements indicate quantum-limited performance. A procedure is given for optimizing the bandwidth for this kind of amplifier, using a linearized circuit simulation while minimizing non-linearities.

We demonstrate a lumped-element Josephson parametric amplifier, using a single-ended design that includes an on-chip, high-bandwidth flux bias line. The amplifier can be pumped into its region of parametric gain through either the input port or through the flux bias line. Broadband amplification is achieved at a tunable frequency ω/2π between 5 and 7 GHz with quantum-limited noise performance, a gain-bandwidth product greater than 500 MHz, and an input saturation power in excess of −120 dBm. The bias line allows fast frequency tuning of the amplifier, with variations of hundreds of MHz over time scales shorter than 10 ns.

Josephson parametric amplifiers (JPAs) with nearly quantum-limited noise performance have become indispensable devices for the measurements of superconducting quantum information. We have developed an all-Nb lumped-element flux-driven JPA operating in the three-wave mixing mode. Our Nb-based JPA comprises Nb/Al-AlO x /Nb Josephson junctions, a parallel-plate capacitor with SiO2 dielectric sandwiched between two Nb layers, a bottom coplanar waveguides layer, and a top Nb wiring layer. We experimentally demonstrate a 20 dB gain over a 190 MHz bandwidth, a mean 1 dB compression of –123 dBm, and near quantum-limited noise performance. This fabrication process can be further used to design impedance transformed parametric amplifiers for multiple-qubit readout.