Superconducting qubit readout enhanced by path signature

TL;DR

This paper introduces a novel method using path signatures to analyze quantum measurement records, significantly improving qubit readout fidelity and state transition detection across various hardware configurations.

Contribution

The study demonstrates that path signatures enhance quantum measurement analysis, offering a new, more expressive feature set for improved qubit state classification and transition detection.

Findings

Significant fidelity improvement across five hardware setups

Path signatures effectively detect and classify state transitions

Enhanced qubit state prediction accuracy

Abstract

Quantum non-demolition measurement plays an essential role in quantum technology, crucial for quantum error correction, metrology, and sensing. Conventionally, the qubit state is classified from the raw or integrated time-domain measurement record. Here, we demonstrate a method to enhance the assignment fidelity of the readout by considering the "path signature" of this measurement record, where the path signature is a mathematical tool for analyzing stochastic time series. We evaluate this approach across five different hardware setups, including those with and without readout multiplexing and parametric amplifiers, and demonstrate a significant improvement in assignment fidelity across all setups. Moreover, we show that the path signature of the measurement record provides an expressive feature set that can be used to detect and classify state transitions that occurred during the measurement, improving the prediction of the qubit state at the end of the measurement. This method has the potential to become a foundational tool for quantum technology.