Quantum key distribution based on arbitrary private states
Karol Horodecki, Michał Horodecki, Paweł Horodecki, Debbie Leung, Jonathan Oppenheim · arXiv (Cornell University) · 2006
We prove unconditional security for a quantum key distribution (QKD) protocol based on distilling pbits (twisted ebits) [quant-ph/0309110] from an arbitrary untrusted state that is claimed to contain distillable key. Our main result is that we can verify security using only public communication -- via parameter estimation of the given untrusted state. The technique applies even to bound entangled states, thus extending QKD to the regime where the available quantum channel has zero quantum capacity. We also show how to convert our purification-based QKD schemes to prepare-measure schemes.