Quantum computer scientists believe quantum computers can solve problems that are intractable for conventional computers. It’s not that quantum computers are like regular computers, but smaller and faster. Rather, quantum computers work according to principles entirely different than conventional computers, and using those principles can solve problems whose solution will never be feasible on a conventional computer.
In everyday life, all our experience is with objects which can be directly simulated by a conventional computer. We don’t usually think about this fact, but movie-makers rely on it, and we take it for granted – special effects are basically just rough computer simulations of events that would be more expensive for the movie makers to create in real life than they are to simulate inside a computer. Much more detailed simulations are used by companies like Boeing to test designs for their latest aircraft, and by Intel to test designs for their latest chips. Everything you’ve ever seen or done in your life – driving a car, walking in the park, cooking a meal – all these actions can be directly simulated using a conventional computer. […]
Now, imagine for the sake of argument that I could give you a simple, concrete explanation of how quantum computers work. If that explanation were truly correct, then it would mean we could use conventional computers to simulate all the elements in a quantum computer, giving us a way to solve those supposedly intractable problems I mentioned earlier. […] Quantum computers cannot be explained in simple concrete terms; if they could be, quantum computers could be directly simulated on conventional computers, and quantum computing would offer no advantage over such computers. […]
Quantum computers work by exploiting what is called “quantum parallelism”. The idea is that a quantum computer can simultaneously explore many possible solutions to a problem. Implicitly, such accounts promise that it’s then possible to pick out the correct solution to the problem, and that it’s this which makes quantum computers tick. […] The problem comes in the second part of the story: picking out the correct solution.