# Securing quantum networking tasks with multipartite Einstein-Podolsky-Rosen steering

## TL;DR

This paper demonstrates that multipartite EPR steering in graph states can be used to secure quantum networks against cloning attacks, ensuring the integrity of quantum information processing even with untrusted measurement devices.

## Contribution

It reveals a no-sharing restriction of multipartite EPR steering in graph states under cloning attacks, enhancing security in quantum networking protocols.

## Key findings

- Only one subsystem exhibits EPR steering after cloning attack.
- Multipartite EPR steering can secure quantum channels against cloning.
- Security holds even with untrusted measurement devices.

## Abstract

Einstein-Podolsky-Rosen (EPR) steering is the explicit demonstration of the fact that the measurements of one party can in influence the quantum state held by another, distant, party, and do so even if the measurements themselves are untrusted. This has been shown to allow one-sided device-independent quantum-information tasks between two remote parties. However, in general, advanced multiparty protocols for generic quantum technologies, such as quantum secret sharing and blind quantum computing for quantum networks, demand multipartite quantum correlations of graph states shared between more than two parties. Here, we show that, when one part of a quantum multidimensional system composed of a two-colorable graph state (e.g., cluster and Greenberger-Horne-Zeilinger states) is attacked by an eavesdropper using a universal cloning machine, only one of the copy subsystems can exhibit multipartite EPR steering but not both. Such a no-sharing restriction secures both state sources and channels against cloning-based attacks for generic quantum networking tasks, such as distributed quantum-information processing, in the presence of uncharacterized measurement apparatuses.