Ask Ethan: Does quantum computation occur in parallel universes?
Briefly

Quantum computers are real, and they really do hold tremendous potential to help us efficiently solve a wide class of problems that conventional computers cannot efficiently solve.
One of the big myths about quantum computers is that they can potentially solve problems that classical computers cannot; that is not true. Any problem that can be simulated on a quantum computer can also be simulated on a classical computer; this is the core of a very famous notion in computer science: the Church-Turing thesis.
Read at Big Think
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