Superconducting qubit readout enhanced by path signature

Kavli Affiliate: Irfan Siddiqi

| First 5 Authors: Shuxiang Cao, Zhen Shao, Jian-Qing Zheng, Mohammed Alghadeer, Simone D Fasciati

| Summary:

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 has features 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.

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