Measurable Improvement in Multi-Qubit Readout Using a Kinetic Inductance Traveling Wave Parametric Amplifier

Published

August 1, 2025

Author(s)

Manuel Beltran, Logan Howe, Andrea Giachero, Michael Vissers, Danilo Labranca, Joel Ullom, Peter Hopkins

Abstract

Superconducting quantum computing benefits significantly from readout chains operating very near the Quantum Limit (QL) of added noise. This is typically achieved using Josephson Parametric Amplifiers (JPAs) which are inherently narrowband and suffer from very low dynamic range -- making them a sub-optimal choice for scaling systems to a large number of qubits. A more appropriate and scalable technology is that of the Traveling Wave Parametric Amplifier (TWPA) which opens the bandwidth up to multi-gigahertz levels. Furthermore, we propose implementing Kinetic Inductance TWPAs (KI-TWPAs) and a further enhancement due to their much larger dynamic range relative to Josephson-based TWPAs. Indeed, prior KI-TWPAs fabricated from a 20nm thick NbTiN film have been operated near to the quantum limit, however, these devices require a pump tone amplitude too large for appropriate control line thermalization for high fidelity superconducting qubit readout. A reduction in the film thickness, to 10nm, has successfully reduced the required pump power and made new KI-TWPAs qubit-compatible. In this work we demonstrate integration of a lower-pump-power KI-TWPA with a multi-qubit device. We perform a direct measurement and comparison of the improvement to the readout fidelity and signal-to-noise ratio (SNR) when the KI-TWPA is the first-stage amplifier (FSA) when compared to a commercial semiconductor (HEMT) amplifier as the FSA. Despite a non-optimal match in the qubit readout cavity frequencies and the KI-TWPA gain bandwidth, we show that with only modest gain we increase the readout fidelity by nearly 2\%, and the SNR by a factor of 1.45. Our measurements show a promising path forward for realizing quantum-limited readout chains in large qubit systems using a single parametric amplifier.

Citation

IEEE Transactions on Applied Superconductivity

Volume

35

Issue

5

Pub Type

Journals

Download Paper

https://doi.org/10.1109/TASC.2024.3525451

Local Download

Keywords

Traveling wave parametric amplifier, kinetic inductance, quantum-limit, noise, quantum computing, multi-qubit

Citation

Beltran, M. , Howe, L. , Giachero, A. , Vissers, M. , Labranca, D. , Ullom, J. and Hopkins, P. (2025), Measurable Improvement in Multi-Qubit Readout Using a Kinetic Inductance Traveling Wave Parametric Amplifier, IEEE Transactions on Applied Superconductivity, [online], https://doi.org/10.1109/TASC.2024.3525451, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958780 (Accessed July 12, 2025)