# How do we detect disturbance on a system when we make a measurement?

### Summary

I am taking an intro. to quantum mechanics course and was taught that superposition exists until we measure the system which makes the wave function of a quantum system collapse. I have a basic understanding of superposition, probabilities etc. However, what I couldn't manage to understand is how we are sure if our measurement does affect the system if we don't know what would happen to the system if we don't measure it.

### A more detailed explanation

I am currently trying to understand quantized energy levels, not just recognize the formula and patterns. So, I have 2 complex numbers that define the probability of an electron to be in either ground or 1st excited state. If we don't measure the system the electron is in superposition. When we measure the electron, its wave function collapses to either ground or 1st excited state, but again how we can be certain on that it hadn't been in the system that we measured? I couldn't find directly answers related to this questions, but rather on the existence of superposition, which in my case I accept. I must be missing a logical explanation, but I can't find.

*actually this postulate is only kinda right-ish, and doesn't work for all types of measurements. In particular it gives inaccurate results for continuous variables like $$x$$ and $$p$$.
• each run gives a different outcome. I couldn't think that this may be the reason, thank you! Apr 8, 2023 at 11:38