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Quantum Cryptography

William P. Risk and Donald S. Bethune

The desire to communicate in secrecy is an ancient one: literature surviving from the time of the Roman Empire describes a substitution cipher used by Julius Caesar; earlier Greek writings describe methods used to conceal confidential military and diplomatic communiqués from the eyes of unauthorized readers. Two millennia later, modern concepts of quantum mechanics are being combined with state-of-the-art optoelectronics to provide a truly novel solution to this ancient problem.