Oraqle: An Empirical Analysis of Qubit Readout and Discriminators in Quantum Error Correction

Quantum error correction (QEC) relies on a continuous cycle of measuring ancilla qubits to detect errors. This process depends entirely on the qubit-state discriminator—the component that converts raw analog signals from the quantum processor into binary syndrome outcomes. Because readout is typically the slowest and most error-prone part of the QEC cycle, it acts as a critical bottleneck for fault-tolerant quantum computing. This paper introduces Oraqle, an end-to-end benchmarking framework designed to evaluate the interplay between readout characteristics, machine learning (ML) discriminator architectures, and overall QEC performance.

The authors developed Oraqle to bridge the gap between raw quantum signal processing and high-level QEC simulation. By using experimentally extracted IQ trace datasets, the researchers systematically evaluated six state-of-the-art ML discriminator architectures (ranging from simple feed-forward networks to complex transformers) across six different QEC codes. The study spans various hardware regimes, from current-generation superconducting devices to projected future hardware, allowing for a comprehensive analysis of how measurement duration and classification accuracy propagate through the stack to affect the logical error rate.

The study reveals three primary insights that challenge conventional design assumptions:

1. Measurement Duration: The readout window can be significantly shortened without a meaningful penalty to the logical error rate, as the majority of the signal information is captured early in the measurement process.
2. Discriminator Complexity: Increasing the complexity of the ML discriminator provides diminishing returns. Because residual errors are largely dictated by the underlying device physics rather than the classification model, simpler models often perform as well as more complex ones in a QEC context.
3. Conditional Impact: The influence of readout quality on logical error rates is highly dependent on the device's position within the QEC landscape, with the sensitivity to readout improvements increasing as hardware matures toward lower physical error rates.