Genuine multipartite entanglement is not a precondition for secure conference key agreement

Abstract

Entanglement plays a crucial role in the security of quantum key distribution. A secret key can only be obtained by two parties if there exists a corresponding entanglement-based description of the protocol in which entanglement is witnessed, as shown by Curty et al (2004). Here we investigate the role of entanglement for the generalization of quantum key distribution to the multipartite scenario, namely conference key agreement. In particular, we ask whether the strongest form of multipartite entanglement, namely genuine multipartite entanglement, is necessary to establish a conference key. We show that, surprisingly, a non-zero conference key can be obtained even if the parties share biseparable states in each round of the protocol. Moreover we relate conference key agreement with entanglement witnesses and show that a non-zero conference key can be interpreted as a non-linear entanglement witness that detects a class of states which cannot be detected by usual linear entanglement witnesses.

5 + 5 pages, 4 figures. v02: Strengthened results, including performance of the family of biseparable states under consideration for the N-BB84 protocol. Section III of supplemental material of v01 removed, as it contained an example state mistakenly claimed to be biseparable

References in corpus (5)

• Quantum cryptography: Public key distribution and coin tossing
• Entanglement detection
• Distillation of secret key and entanglement from quantum states
• Entanglement Certification $-$ From Theory to Experiment
• Quantum Conference Key Agreement: A Review

Cited by in corpus (10)

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• Genuine multipartite entanglement of quantum states in the multiple-copy scenario
• Boosting device-independent cryptography with tripartite nonlocality
• Experimental Measurement-Device-Independent Quantum Cryptographic Conferencing
• Certifying Quantum Separability with Adaptive Polytopes
• Continuity of robustness measures in quantum resource theories
• A scheme for multipartite entanglement distribution via separable carriers
• Investigating controlled teleportation capability of quantum states with respect to $k$-separability
• Genuine multipartite entanglement is not necessary for standard device-independent conference key agreement
• Spanning-tree-packing protocol for conference key propagation in quantum networks