Making quantum encryption practical
One of the many promising applications of quantum mechanics in the information sciences is quantum key distribution (QKD), in which the counterintuitive behavior of quantum particles guarantees that no one can eavesdrop on a private exchange of data without detection.
As its name implies, QKD is intended for the distribution of cryptographic keys that can be used for ordinary, nonquantum cryptography. That’s because it requires the transmission of a huge number of bits for each one that’s successfully received. That kind of inefficiency is tolerable for key distribution, but not for general-purpose communication.
Also, because QKD depends on the properties of individual light particles — photons — it’s very vulnerable to signal loss, which is inevitable over large enough distances. Although QKD systems have been built — some commercially — they generally work across distances of only 100 miles or so.
