Question: How is the quantum computer better than today's computers?

Euan Allen answered on 19 Jun 2016:

That’s a great question 483eadf46.

A quantum computer is only better than today’s computers for some specific problems, and we’re still discovering new problems that they are good for. Some example problems include searching for an item in a list, ray tracing in computer graphics, some machine learning algorithms, and some engineering modelling techniques.

The reason the quantum computer is better at these tasks than a classical computer is because the quantum computer has access to some very special phenomenon that occur due to quantum mechanics. Take for example the difference between a classical bit, and a quantum bit (we call this a qubit). The classical bits inside your laptop PC are lines of zeroes and ones that are used to send information around your processor and compute useful tasks. Any individual bit can be either a one or a zero at any point in time.

A qubit is a very similar item, and for most cases can take a value of zero or one, just like the classical bit. However, using quantum mechanics we can set this qubit to be in what we call a superposition, where it acts like it is both a zero and a one at the same time! This is one of the outcomes of the ‘weirdness’ of quantum mechanics. It turns out that if you give yourself access to this behaviour (along with some others), then some computational tasks become easier (either they can be done faster, or they need a smaller computer). This is why a quantum computer is better than a classical one is some cases.