Source: http://www.vox.com/2014/4/9/5588236/quan...

A quantum computer would instead rely on "qubits" — particles that shift their state based on the weird rules of quantum mechanics.

A qubit could be any number of things. It could be a photon, moving in a wave that's oriented horizontally or vertically. Or it could be an atom with a nucleus that's spinning either clockwise or counter-clockwise. The important thing is that the qubit needs to be a particle that's subject to the strange laws of quantum physics, and has two different forms, which are coded as 0 and 1.

Because of the rules of quantum physics, these qubits could in fact be both 0 and 1 at the same time. A quantum computer would involve multiple qubits that are functionally linked together — with the state of one qubit affecting the state of other qubits. A practical quantum computer would be built out of thousands or millions of these qubits all linked together.

Because of the uncertainty built into the state of each qubit at any given time, this would generate a massive combination of 0's and 1's — much more massive than any normal computer is capable of. Each combination would produce interference and entanglement between different sets of qubits, leading to dramatically larger sets of data that can be held within the system.

When the user of the quantum computer goes to "check" on the status of the qubits, however, they would only appear to be 0s or 1s. (Remember, superposition can't be observed.) So the qubits would effectively be processing problems among themselves, and when the computer user went to check on them, they'd give an answer.

The system is probabilistic — so the computer users would need to keep "checking" the qubits over and over, which would eventually get them closer to the correct answer.