Final High-Fidelity Down-Conversion Source for Secure Communications Using On-Demand Single Photons

Secure communication over long distances requires robust encryption. While current encryption algorithms exist using classical methods, there are no unconditionally secure methods of distributing encryption keys classically. However, by exploiting the quantum nature of individual photons, quantum key distribution (QKD) can be proven as an unconditionally secure method for the distribution of encryption keys. Because QKD operates via the transmission and detection of single photons, there are major challenges for practical use in terms of both key generation rate and the maximum distance over which a secret key can be established.