Quantum computers are fundamentally different from classical computers because the physics of quantum information is also the physics of possibility. Quantum algorithms can perform this task exponentially faster than the best known classical strategies, rendering some forms of modern cryptography powerless to stop a quantum codebreaker.

This is because the most common form of Internet security, public key cryptography, relies on certain math problems (like factoring numbers that are hundreds of digits long) being effectively impossible to solve. With 5,000 guesses a quantum computer could search through a phonebook with 25 million names.Īlthough quantum search is impressive, quantum factoring algorithms pose a legitimate, considerable threat to security. A quantum search algorithm only needs to guess 100 times. If the phonebook has 10,000 entries, on average you'll need to look through about half of them-5,000 entries-before you get lucky.

To understand the power of a quantum search, consider classically searching a phonebook for the name which matches a particular phone number. To date, the two most promising uses for such a device are quantum search and quantum factoring. A largescale, working quantum computer-the kind of quantum computer some scientists think we might see in 50 years-would be capable of performing some tasks impossibly quickly. By studying this relationship between quantum theory and information, it is possible to design a new type of computer- a quantum computer. To be more specific, the field of quantum information studies the implications that quantum mechanics has on the fundamental nature of information. Quantum information is the physics of knowledge.

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