**Hardly a headline to grab the popular imagination. But when it’s done by a quantum computer – and one that’s scalable – it’s time to take notice.**

**A paper published today in Science describes a five-atom quantum computer that can factor numbers – that is, start with a number and find numbers that, when multiplied, equal that first number. For instance, 15 factors into three times five.**

**It's also a striking illustration of how quantum computers will smash today's internet encryption – when they arrive, that is. **

**Computerised factoring is not new – quantum computers have factored numbers before (and those much bigger than 15). The key point here, though, is the new design can be upscaled to much more powerful versions simply by adding atoms.**

**Many of the world’s public key security systems, which encrypt online banking transactions and the like, operate on a simple principle: that it’s easy to multiply two large prime numbers to generate a gigantic number.**

**But given the gigantic number, it’s next to impossible to work out its factors, even using a computer.**

**In March 1991 the encryption company RSA set a challenge – they published a list of very large numbers and announced cash awards for whoever could factor them. The prizes went from $1,000 for factoring a 100-digit number, up to $200,000 for a 617-digit number.**

**A quarter of a century later, most of those numbers remain uncracked. **

**But with a large enough quantum computer, factoring huge numbers – even those 600 digits long – would be child’s play.**

Category: News

Written by Kim Burrafato

Published on Saturday, 05 March 2016 11:56

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