Any computer should be able to do two things: store information in the form of bits (0s and 1s), and offer a way to alter the bits in accordance with instructions (using logic gates. Thus writes Vishal Sahni in Quantum Computing ( http://www.tatamcgrawhill.com/).
“Everything a computer does — whether synthesising speech, calculating the billionth digit of pi or beating Garry Kasparov at chess — ultimately comes about through the transformation of bits by gates,” he explains.
“Could subatomic particles store bits? Could they form gates?” To find answers to these questions, you need to enter the world of quantum computers, which operate according to the rules of quantum mechanics governing ‘the world of the very small: the waves and particles of subatomic physics’.