Device-independent quantum key distribution secure against collective attacks

TL;DR

This paper provides a detailed security proof for a device-independent quantum key distribution protocol that is secure against collective attacks, relying on Bell inequality violations and quantum theory's full structure.

Contribution

It offers the first detailed security proof for a DIQKD protocol against collective attacks using the full quantum formalism.

Findings

Security proof exploits quantum theory's full structure

Protocol secure against collective attacks with Bell inequality violation

Discussion of loopholes in Bell experiments

Abstract

Device-independent quantum key distribution (DIQKD) represents a relaxation of the security assumptions made in usual quantum key distribution (QKD). As in usual QKD, the security of DIQKD follows from the laws of quantum physics, but contrary to usual QKD, it does not rely on any assumptions about the internal working of the quantum devices used in the protocol. We present here in detail the security proof for a DIQKD protocol introduced in [Phys. Rev. Lett. 98, 230501 (2008)]. This proof exploits the full structure of quantum theory (as opposed to other proofs that exploit the no-signalling principle only), but only holds again collective attacks, where the eavesdropper is assumed to act on the quantum systems of the honest parties independently and identically at each round of the protocol (although she can act coherently on her systems at any time). The security of any DIQKD protocol necessarily relies on the violation of a Bell inequality. We discuss the issue of loopholes in Bell experiments in this context.