Delayed-choice quantum cryptography

摘要

Quantum cryptography is a method of communicating securely, the secrecy of which is guaranteed by the laws of physics and information theory. Current implementations suffer from relatively short ranges and low data rates. We are developing a system that modifies the usual protocol by incorporating elements of special relativity. The result is that in principle, every detected photon can be used in the final key, thus doubling or tripling the possible data rate. Our delayed-choice quantum cryptography (DCQC) system works by storing the photon sent to Bob in a low-loss optical delay line until a classical signal from Alice informs him which measurement basis to use.