An illustrated guide to quantum computing, including qubits, algorithms, challenges, government support, and “Q-day”, when a quantum computer cracks encryption
They call it Q-day. That is the day when a robust quantum computer will be able to crack the most common encryption method used to secure our digital data. Q-day will have massive implications for all internet companies, banks and governments — as well as our own personal privacy. We know that this will happen one day. The only question is when. For the moment, quantum computers, which exploit the spooky physics of subatomic particles, remain too unstable to perform sophisticated operations for long. IBM’s Osprey computer, thought to be the most powerful quantum computer yet developed, only has 433 qubits (or quantum bits) when most computer scientists consider it would take 1mn to realise the technology’s potential. That may still be a decade away. But in 1994 the American mathematician Peter Shor wrote an algorithm that could theoretically run on a powerful quantum computer to crack the RSA encryption protocol most commonly used to secure online transactions. The RSA algorithm exploits the fact that while it is very easy to multiply two large prime numbers, no one has yet discovered an efficient way for a classical computer to perform the calculation in reverse. Shor showed how a quantum computer could do so relatively easily.