Qubits and Quantum Computation

Today's computer work by manipulating bits that exist in one of two states: 0 or 1. However, Quantum computers are not limited to only these two basic states. They encode information as quantum bits, or qubits which can also exists in superpositions: effectively this means that the qubit is both in state 0 and state 1.

Picture From http://www.quantiki.org/

For example, any classical register composed of three bits can store only one out of the eight different number combinations in a given time. A quantum register on the other hand is able to store all eight different numbers simultaneously in a quantum superposition.

Once a quantum register is prepared in a superposition of different numbers, operations can be performed on all of them. In brief, quantum processors can perform many different calculations in parallel. This has impact on the execution time and the memory required in the process of computation. According to physicist David Deutsch, this parallelism allows quantum computers to work on a million computations at once while your desktop PC works on one.

Because quantum computers contain these multiple states at once, it has the potential to be far more powerful than today's most powerful supercomputers.

(Qubits: Atoms that work together to act as computer memory and processor.)

(Superposition: Principle of quantum theory that describes the concept about the nature and behavior of matter and forces at the atomic level. It claims that any object is actually in all possible states simultaneously as long as we don't check. The measurement itself causes the object to be limited to a single possibility. Definition from Whatis.com)