English physicist David Deutsch publishes the article: “Quantum theory, the Church–Turing principle, and the universal quantum computer.” It lays the foundations of quantum computing, where quantum computers can handle multiple calculations simultaneously in a superposition of states. In Hugh Everett III’s interpretation, quantum computers do so in different universes, in what Everett called the Multiverse. But how to program these computers? It would take a decade, and in 1994, Peter Shor of AT&T Bell Labs in New Jersey defined a program for quantum computers to factorize large numbers into prime factors. But by the mid-1990s, he still didn’t have a quantum computer at his disposal. If quantum computers could attack RSA Public Key Cryptography, there would be global consequences. And quantum cryptography would suddenly become essential to guaranteeing information security and reestablishing codemakers as victorious over codebreakers, in a struggle that has continued for thousands of years. A struggle that, with Quantum Cryptography, could come to an end. Using quantum superpositions or quantum entanglement and transmitting information in quantum states, it is possible to implement a communications system that detects eavesdropping.
