Boosting device-independent cryptography with tripartite nonlocality

Revealing Hidden Genuine Tripartite Nonlocality

Nonlocal correlations arising from measurements on tripartite entangled states can be classified into two groups, one genuinely 3−way nonlocal and other local with respect to some bipartition. Still, whether a genuinely tripartite entangled quantum state can exhibit genuine 3−way nonlocality, remains a challenging problem so far as measurement context is concerned. Here we introduce a novel app...

Graphical Methods in Device-Independent Quantum Cryptography

We introduce a framework for graphical security proofs in device-independent quantum cryptography using the methods of categorical quantum mechanics. We are optimistic that this approach will make some of the highly complex proofs in quantum cryptography more accessible, facilitate the discovery of new proofs, and enable automated proof verification. As an example of our framework, we reprove a...

High-rate measurement-device-independent quantum cryptography

Implications of Superstrong Nonlocality for Cryptography

Non-local boxes are hypothetical “machines” that give rise to superstrong non-local correlations, leading to a stronger violation of Bell/CHSH inequalities than is possible within the framework of quantum mechanics. We show how non-local boxes can be used to perform any two-party secure computation. We first construct a protocol for bit commitment and then show how to achieve oblivious transfer...

Device-independent security of quantum cryptography against collective attacks.

We present the optimal collective attack on a quantum key distribution protocol in the "device-independent" security scenario, where no assumptions are made about the way the quantum key distribution devices work or on what quantum system they operate. Our main result is a tight bound on the Holevo information between one of the authorized parties and the eavesdropper, as a function of the amou...