Scalable multiparty steering based on a single pair of entangled qubits

TL;DR

This paper introduces a scalable quantum steering method that enables one party to steer many others using only a single entangled qubit pair, verified experimentally with three parties, advancing quantum network verification.

Contribution

The work demonstrates multiparty quantum steering using only one entangled qubit pair, simplifying the requirements for scalable quantum network verification.

Findings

Achieved loophole-free multiparty quantum steering with a single entangled pair.

Experimentally demonstrated steering among three parties.

Provided a practical approach for scalable quantum nonlocality verification.

Abstract

The distribution and verification of quantum nonlocality across a network of users is essential for future quantum information science and technology applications. However, beyond simple point-to-point protocols, existing methods struggle with increasingly complex state preparation for a growing number of parties. Here, we show that, surprisingly, multiparty loophole-free quantum steering, where one party simultaneously steers arbitrarily many spatially separate parties, is achievable by constructing a quantum network from a set of qubits of which only one pair is entangled. Using these insights, we experimentally demonstrate this type of steering between three parties with the detection loophole closed. With its modest and fixed entanglement requirements, this work introduces a scalable approach to rigorously verify quantum nonlocality across multiple parties, thus providing a practical tool towards developing the future quantum internet.