Complete Self-Testing of a System of Remote Superconducting Qubits

TL;DR

This paper demonstrates a complete, device-independent self-testing protocol for superconducting qubits, certifying entanglement and measurement fidelity over 30 meters without assumptions, advancing scalable quantum computing and communication.

Contribution

It introduces the first self-testing method for superconducting qubits, including Bell pair generation and measurements, enabling device-independent certification in practical quantum systems.

Findings

Achieved an average CHSH S-value of 2.236 in 17 million trials.

Certified Bell state fidelity of at least 58.9% with 99% confidence.

Certified measurement fidelity of at least 89.5% with 99% confidence.

Abstract

Self-testing protocols enable the certification of quantum systems in a device-independent manner, i.e. without knowledge of the inner workings of the quantum devices under test. Here, we demonstrate this high standard for characterization routines with superconducting circuits, a prime platform for building large-scale quantum computing systems. We first develop the missing theory allowing for the self-testing of Pauli measurements. We then self-test Bell pair generation and measurements at the same time, performing a complete self-test in a system composed of two entangled superconducting circuits operated at a separation of 30 meters. In an experiment based on 17 million trials, we measure an average CHSH (Clauser-Horne-Shimony-Holt) S-value of 2.236. Without relying on additional assumptions on the experimental setup, we certify an average Bell state fidelity of at least 58.9% and an average measurement fidelity of at least 89.5% in a device-independent manner, both with 99% confidence. This enables applications in the field of distributed quantum computing and communication with superconducting circuits, such as delegated quantum computing.