16 June 2015, Theoretical Computer Science Seminar, Jeremy Ribeiro

We use the entanglement sampling techniques developed in (Dupuis et al., 2015) to find a lower bound on the entanglement needed by a coalition of cheaters attacking the quantum postition verification protocol using the four BB84 states (QPVBB84) in the scenario where the cheaters have no access to a quantum channel but share a (possibly mixed) entangled state Φ. For a protocol using n qubits, a necessary condition for cheating is that the max-relative entropy of entanglement E_max(Φ) ≥ n − O(log n). This improves previously known best lower bound by a factor approx. 4, and it is essentially tight, since the protocol is vulnerable to a teleportation-based attack using n − O(1) ebits of entanglement.

For more information, see the article at http://arxiv.org/abs/1504.07171 or contact Christian Schaffner (c.schaffner at uva.nl).