Quantum computers rely on the famous weirdness of quantum mechanics to perform certain sorts of calculation far faster than any conceivable classical machine. Their fundamental unit is the “qubit”, a quantum analogue of the ones and zeros that classical machines manipulate. By exploiting the quantum-mechanical phenomena of superposition and entanglement, quantum computers can perform some forms of mathematics—though only some—far faster than any conceivable classical machine, no matter how beefy.
In 1994 Peter Shor, a mathematician then working at Bell Laboratories, in America, came up with a quick and efficient way to find a number’s prime factors. The only catch was that for large numbers his method—dubbed Shor’s algorithm—needs a quantum computer to work.
Big quantum computers will have applications in fields such as artificial intelligence and chemistry. But it is the threat posed by Shor’s algorithm that draws most public attention. Large organisations may be able to get around the problem using so-called quantum cryptography. This detects eavesdroppers in a way that cannot be countered. But it is expensive, experimental and unsuitable for the internet because it must run on a special, dedicated network. For most people, therefore, the best hope of circumventing Shor’s algorithm is to find a bit of one-way maths that does not give quantum computers an advantage.
But translating a piece of maths into usable computer code and then delivering it to the zillions of machines that will need updating will not be easy.
Despite—or perhaps because of—the information-technology industry’s obsession with novelty, the internet resembles ancient cities like Rome and Istanbul, with modern structures built atop forgotten layers of old, unmaintained code.
Read the complete article in The Economist here.