# Can quantum computers compute a vast number of possible solutions simultaneously?

https://www.roche.com/quantum-computing.htm

They are not constrained to stepwise calculations but, rather, can compute a vast number of possible solutions simultaneously—and at a speed that is far beyond anything we can imagine.

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Isn’t this wrong? AFAIK quantum computers **cannot** compute a vast number of possible solutions simultaneously. **A Quantum Computer is not a parallel computer**. It is true that the wave function will exist in a superposition of states before measurement, but when we make a measurement it will collapse to a definite state. And measurements is all we can do.

From scott aaronson’s blog (https://www.scottaaronson.com/blog/)

*If you take just one piece of information from this blog:
Quantum computers would not solve hard search problems
instantaneously by simply trying all the possible solutions at once.*

curious to know what other experts think

If that wasnt true, wed be simulating the universe on our commodore 64’s, what do you think?

The picture that a quantum computer runs many calculations in parallel is not completely wrong, but it is still somewhat misleading.

From this simple picture people often think that quantum computers can run pretty much any computation efficiently. However, this is not true. In fact the space of problems quantum computers can solve efficiently is rather limited. Probably the most relevant one is breaking asymmetric encryption. Many other problems, like for example most optimization problems can actually not be solved efficiently on a quantum computer.

If you want to know more have a look at this article:

https://medium.com/twodigits/3-reasons-quantum-computing-is-overrated-9d87d11aa248