So, in quantum computing, each qbit has a 50/50 chance of being in either the state of 1 or 0 when you measure it. Simple enough.

But I've heard reports a while ago about some company having successfully added two relatively small numbers and gotten out the right answer the majority of the time. The question I am trying to solve is: How? How would you verify a quantum result (without assuming you have the answer already available that you can compare it to)?

That, however, is not what I'm asking of this Stack Exchange. Instead, I am wanting to know what search terms in Google I can use to find this answer. "how to verify quantum computing results" doesn't turn up anything more than 1 academic paper (which I am actually reasonably confident has the answer I'm looking for). At least with the search, I get nothing more that is relevant to what I'm actually looking for.

Thus why I come here in hopes that someone might actually know what I would need to search to get more relevant results.

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    $\begingroup$ It's not true that each qubit has a 50/50 chance of being in each state. It depends on the state of the qubit. $\endgroup$ Oct 24, 2019 at 10:33

2 Answers 2


The answer is, when working with sufficiently small numbers, we can simulate the quantum process on a classical computer. It might take exponentially longer on the classical computer, but for small numbers, that's still feasible (the exponential of a small number is still not too large).

See Question 6 at Scott Aaronson's FAQ (https://www.scottaaronson.com/blog/?p=4317) as well as part (2) of https://www.scottaaronson.com/blog/?p=4372.


My logic may be off, but here is my take. Consider the following:

  1. We want to find possible seeds for an existing and known hashed value.

  2. We have a superposition of all possible seed values.

  3. We run the superposition through the hashing algorithm to generate a waveform.

  4. Run grovers algorithm (or similar) on waveform to reveal likely hash values

Verification process:

5. Remove values from the superposition that are not "near" a correct value.

6. Run the algorithm again.

7. Repeat until the waveform is a straight line representing the correct state.
  1. The seed values remaining in the superposition have a 100% chance of generating the desired hash value.
  • $\begingroup$ (Try prepending - before Verification process:) $\endgroup$
    – greybeard
    Jun 30, 2021 at 4:48

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