Real-time preparation and verification of nonstabilizer states

TL;DR

This paper demonstrates a real-time quantum state verification protocol for three-qubit nonstabilizer states, integrating state preparation and verification to efficiently generate and validate high-fidelity entangled states in quantum information processing.

Contribution

It introduces the first experimental implementation of QSV actively combined with state preparation, enhancing real-time quantum state engineering capabilities.

Findings

Achieved 97.07% fidelity with 9 measurement settings and 10^4 samples.

Verified the efficiency of the protocol with favorable scaling of required copies.

Confirmed high fidelity via quantum state tomography with approximately 10^6 measurements.

Abstract

Entanglement lies at the heart of quantum information science, serving as a key resource for quantum communication, computation, and metrology. Consequently, high-precision entangled state preparation and efficient verification are essential for practical quantum technologies. Quantum state verification (QSV) has recently gained much attention as an efficient and experiment-friendly approach for verifying entangled states. In this work, we experimentally demonstrate a QSV protocol for verifying three-qubit nonstabilizer $W$ state via a modified homogeneous strategy. Notably, our implementation extends QSV beyond its standard role by integrating the state preparation process, thus guiding and validating the real-time generation of high-fidelity target states. Specifically, we realize the efficient verification with a favorable scaling of the required number of copies versus infidelity as $-1.39$, outperforming the standard quantum limit of $-2$. Meanwhile, a fidelity of $97.07(\pm 0.26)\%$ via direct estimation is achieved using only $9$ measurement settings and $10^4$ samples, which is independently confirmed by quantum state tomography to be $98.58(\pm 0.12)\%$ with approximately $10^6$ measurements. This work presents the first experimental demonstration of QSV actively assisted with state preparation, establishing it as a powerful and resource-efficient alternative to full tomography for real-time quantum state engineering.