Qubit ZooQubit Readout is a classical hardware readout approach for quantum computing hardware. Source: latex text.
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 , 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 in Y-factor measurements, both lower than the 53% device. The 70% device has the highest gain, but qubit readout SNR and assignment fidelity instead peak at 60%. Using this method, we map against HEMT LNA dc power consumption for each device. 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 , about 1mW is needed to maintain . Across all four devices, is reached with as little as about 0.3mW, 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.
Key Findings
Links
- arXiv: 2609.07250
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