India, Aug. 10 -- Geeks call it Q-Day. The rest of the world calls it doomsday.

But, what's so dreadful in the Q? It stands for quantum computer - one that's more powerful than any built yet - and the day is when such a device would shatter the world of privacy and security.

And, how would it be possible? A bravura act of maths, involving separation of some very large numbers, say, running hundreds of digits, into their prime factors. These numbers could crack open all the sensitive information stored under digital locks.

A quantum computer can fundamentally undermine the encryption protocols that governments and businesses have trusted for decades by resolving calculations that would take more than 10,000 years in less than 10 minutes...