University of Cambridge
Quantum key distribution protocols typically make use of a one-way quantum channel to distribute a shared secret string to two distant users. However, protocols exploiting a two-way quantum channel have been proposed as an alternative route to the same goal, with the potential advantage of outperforming one-way protocols. Here, the authors provide a strategy to prove security for two-way quantum key distribution protocols against the most general quantum attack possible by an eavesdropper. They utilize an entropic uncertainty relation, and only a few assumptions need to be made about the devices used in the protocol.