## computer science

What's stopping us from building useful quantum computers? And how long until we'll have them?

An untapped resource could provide the magic needed for quantum computation — and perhaps even open the door to time travel.

Here's a brief introduction to the possible future of computing.

Why it's hard to build quantum computers and what can be done about it.

A team of computer scientists has found a weakness in the world's most popular anonymity service.

When you transmit information long-distance there is always a chance that some of it gets mangled and arrives at the other end corrupted. Luckily, there are clever ways of encoding information which ensure a tiny error rate, even when your communication channel is prone to errors.

Computers represent information using bits — that's 0s and 1s. It turns out that Claude Shannon's *entropy*, a measure of information invented long before computers became mainstream, measures the minimal number of bits you need to encode a piece of information.

Yesterday's refusal by the UK government to posthumously pardon Alan Turing makes sad news for maths, computer science and the fight against discrimination. But even if symbolic gestures are, symbolically, being rebuffed, at least Turing's most important legacy — the scientific one — is going stronger than ever. An example is this week's announcement that scientists have devised a biological computer, based on an idea first described by Turing in the 1930s.