When two or more atoms or subatomic particles are entangled, any change to one is immediately reflected by the same change in the other regardless of the physical distance between them. Researchers have demonstrated that quantum computers have the potential to be much faster than normal computers for certain tasks like factoring and searching databases. Many researchers have argued that entanglement is the reason quantum computers will be more efficient. But some computer scientists who are working on quantum algorithms are questioning that assumption. David A. Meyer, a research professor in the mathematics department at University of California in San Diego, has demonstrated that, contrary to appearances, a particular quantum search algorithm does not use entanglement.
Interference is the interaction of two or more waves.
When atoms and subatomic particles are in their quantum states, they exist as waves. If you start waves from two sides of a pool that make a corner, you'll get points where they reinforce so that the waves will be higher and points where they cancel out so the surface will be flat. Atoms and particles spin in one of two directions, up or down, which can represent the ones and zeros of binary computing. A particle has a probability of spinning in either direction when it is in its quantum state. A quantum computer acts on a set of particles by influencing the probabilities of the particles' spins so that when the particles leave their quantum state the resulting spin directions represent a specific number.