Quantum Cryptography

History repeats itself. Quantum cryptography has started a revolution of quantum computing and has repeated the days of Einstein's research paper on “Theory of Relativity,” which changed the world's perceptions of physics completely written based on Newton's laws. Quantum cryptography is going to change the definition of computers right from scratch. The last century was witness of a space race between US and USSR. This century would be witness of quantum computing race between US and China. It has changed the dimensions of operating systems, software, hardware, databases, and applications. Quantum computers are in a phase to replace the conventional computers and they are reaching to the level called quantum supremacy. The chapter covers the details of the basic principles and work methodology of quantum cryptography, the contribution of various pioneers, advantages over classical cryptography, its applications, future scope, and limitations simultaneously. The chapter covers the contribution of leading countries and organizations in quantum revolution.