I’ve been brushing up on my quantum physics and quantum information science lately, and thought it would be good practice for me to give a little introduction to the idea of quantum cryptography, and one of the first strategies proposed to do it. “Cryptography,” of course, refers to sending coded messages between two people, and the “quantum” part refers to using the inherent properties of quantum physics to make messages harder to crack. This post, then, will be a little bit about the concepts of cryptography and a little bit about the concepts of quantum physics.
We’ll talk about the first protocol for such quantum cryptography first introduced by Bennett and Brassard in 1984, referred to as the BB84 protocol1. My discussion follows my recent read of Stephen Barnett’s book on Quantum Information, which is a very good introduction for physics folks with some background in math and quantum mechanics. The description here, however, will be my own understanding and interpretation, subject to my own still growing understanding of the subject.
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