Picture-perfect Quantum Key Distribution

Understand

We provide a new way to bound the security of quantum key distribution using only two high-level, diagrammatic features of quantum processes: the compositional behavior of complementary measurements and the essential uniqueness of purification.

• We begin by demonstrating a proof in the simplest case, where the eavesdropper doesn't noticeably disturb the channel at all and has no quantum memory.
• We then show how this approach extends straightforwardly to account for an eavesdropper with quantum memory and the presence of noise.