Security proof for Round Robin Differential Phase Shift QKD

摘要

We give the first information-theoretic security proof of the `Round RobinDifferential Phase Shift' Quantum Key Distribution scheme. Our proof consistsof the following steps. We construct an EPR variant of the scheme. We identifyEve's optimal way of coupling an ancilla to an EPR qudit pair under theconstraint that the bit error rate between Alice and Bob should not exceed avalue $\beta$. We determine, as a function of $\beta$, which POVM measurementon the ancilla Eve has to perform in order to learn as much as possible aboutAlice's bit. It turns out that Eve's potential knowledge is much smaller than suggested inexisting security analyses.