Qubit-Based Benchmarking of InP HEMT LNAs: Readout Fidelity Versus Power Consumption
Abstract
High-fidelity single-shot readout of superconducting qubits is essential for fault-tolerant quantum computation. Without a quantum-limited amplifier such as a Josephson parametric amplifier, the cryogenic high-electron-mobility-transistor (HEMT) low-noise amplifier (LNA) at the 4 K stage is the dominant noise source in the readout chain. HEMT LNAs are conventionally characterized by Y-factor measurements of the noise temperature TN, independently of the quantum measurement they ultimately serve. Here we present a qubit-in-the-loop benchmarking method. The method uses the two-dimensional IQ histogram of single-shot readout as a direct figure of merit. We apply it to three state-of-the-art cryogenic InP HEMT LNAs with 53\%, 60\%, and 70\% channel indium content, together with a commercial reference amplifier. The 60\% and 70\% devices have similar TN in Y-factor measurements, both lower than the 53\% device. The 70\% device has the highest gain, but qubit readout SNR and assignment fidelity ℱa instead peak at 60\%. Using this method, we map ℱa against HEMT LNA dc power consumption for each device. ℱa does not simply saturate with increasing power. For several devices it declines above a device-dependent power well below typical operating points. For the 60\% device, which has the highest overall ℱa, about 1~mW is needed to maintain ℱa > 85%. Across all four devices, ℱa > 80% is reached with as little as about 0.3~mW, roughly an order of magnitude below typical operating points. These results establish a qubit-referenced benchmarking methodology and provide practical guidance for amplifier selection and bias in power-constrained multi-qubit readout systems.
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BibTeX
@misc{li2026qubitbased,
title = {{Qubit-Based Benchmarking of InP HEMT LNAs: Readout Fidelity Versus Power Consumption}},
author = {Junjie Li},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.07250},
eprint = {2609.07250},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07250},
}
RIS
TY - UNPB
TI - Qubit-Based Benchmarking of InP HEMT LNAs: Readout Fidelity Versus Power Consumption
AU - Junjie Li
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.07250
UR - https://arxiv.org/abs/2609.07250
AB - High-fidelity single-shot readout of superconducting qubits is essential for fault-tolerant quantum computation. Without a quantum-limited amplifier such as a Josephson parametric amplifier, the cryogenic high-electron-mobility-transistor (HEMT) low-noise amplifier (LNA) at the 4 K stage is the dominant noise source in the readout chain. HEMT LNAs are conventionally characterized by Y-factor measurements of the noise temperature T_N, independently of the quantum measurement they ultimately serve. Here we present a qubit-in-the-loop benchmarking method. The method uses the two-dimensional IQ histogram of single-shot readout as a direct figure of merit. We apply it to three state-of-the-art cryogenic InP HEMT LNAs with 53\%, 60\%, and 70\% channel indium content, together with a commercial reference amplifier. The 60\% and 70\% devices have similar T_N in Y-factor measurements, both lower than the 53\% device. The 70\% device has the highest gain, but qubit readout SNR and assignment fidelity ℱ_a instead peak at 60\%. Using this method, we map ℱ_a against HEMT LNA dc power consumption for each device. ℱ_a does not simply saturate with increasing power. For several devices it declines above a device-dependent power well below typical operating points. For the 60\% device, which has the highest overall ℱ_a, about 1~mW is needed to maintain ℱ_a > 85%. Across all four devices, ℱ_a > 80% is reached with as little as about 0.3~mW, roughly an order of magnitude below typical operating points. These results establish a qubit-referenced benchmarking methodology and provide practical guidance for amplifier selection and bias in power-constrained multi-qubit readout systems.
ER -