computer science
A closer look at one of the simplest quantum algorithms. 
What will quantum computers be able to do that ordinary computers can't do? 
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 longdistance 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. 