Summary on Quantum Cryptography or Quantum Key Distribution
The key problem of classical cryptography is secret key transfer or secret key distribution. Two legitimate users who share no secret information initially must use some reliable and secure channel to communicate the secret key before they can exchange other secret messages. There is no way, in technical point of view, to protect such communication against eavesdropping and even simply detect confidently whether such eavesdropping activities existed on the channel.
In the intersection of quantum mechanics and information theory, there came quantum cryptography, which is a science using a famous law of physics, Heisenberg’s uncertainty principle applying on polarized photons. The most important and most recognized feature of quantum cryptography theory in practice so far is solving the secret key distribution problem.
The current unique contribution of quantum key distribution is that it provides a mechanism enabling two communicating parties over a private channel automatically detect eavesdropping and that even no useful information can leak to the eavesdroppers. Yet quantum cryptography technology still cannot prevent such eavesdropping in the first hand. However, it forces eavesdroppers to invest in quantum computing technology (which is another theoretical/applied research area coming near to reality, say, multi-bit quantum computers) for new eavesdropping strategies.
In less than 2 decades, researchers have developed the working systems from only a modest 30-centimeter link between two computers in the lab at IBM in 1984, into long distance fiber optics links of more than 20-kilometer. Experts hope that the current technology will eventually expand the open air distance communication capability to a range of over 1000km, which will be good enough for communication between ground stations and a low-orbit satellite network, which may allow for worldwide coverage. Expectedly, new engineering and physical technology will improve the distance more dramatically within next decade.
Quite a few government & private research institutions in the US and European Unions are playing a big role in R&D of this new cryptographic breakthrough, such as DARPA, Los Alamos National Lab, NSA, IBM, NIST, European Space Agency, British Defence Research Agency, British Telecom Laboratories, Swiss Telecom, John Hopkins University, Georgia Institute of Technology, University of Geneva (Switzerland)… Entering the pictures are even private companies, such as MagiQ Technologies (NY), Quantique (Geneva), QinetiQ (England)… who recently are introducing commercial products using quantum cryptographic technology for secure communications at a reasonable price.
summary, quantum cryptography technology has already been developed out of the
experimental research lab to start emerging into the real life to enhance
secure communications against eavesdropping activities.