So, I guess that you have heard about quantum mechanics. No? Well it is a branch of Theoretical Physics. Quantum Mechanics deal with the study of understanding the behavior of matter on the scale of sub-atomic particles.
Well quantum computing is the study (right now mostly theoretical study) of computing systems using the phenomenons of quantum computing, like superposition. Quantum Computers don’t have the same mechanism as the normal digital computers. The computers that we use work on binary (0 & 1) but quantum computers work on what is known as qubits which follow the laws of superposition.
David Deutsch and Richard Feynman have done great deal of work. In fact it was Feynman who envisioned quantum computing systems.
Below is a video Dr. Michio Kaku explaining a quantum computer (No! You won’t be an expert in Quantum Computing after watching this video!)
What good do quantum computers do?
The biggest advantage of quantum computing is that quantum computers are incredibly faster than classical computers. Also we can simulate quantum algorithms on classical computers, but no classical computer in the present world can solve the problems that a quantum computer can solve even if it runs for as long as the age of our universe (or your universe – if you are speaking from a parallel universe! Or if you are currently on holiday to another one!).
Quantum computers can factor pretty large numbers and our present day classical cryptography is heavily based on classical computers inability to factor large numbers – so yes, we will need to tighten up security, because – Kein System Ist Sicher.