I think one of the appeals to actual physicists who do experiments is that is how things are usually set up - there's some equipment that makes a measurement and the Schrödinger equation stuff till collapse thing gives the correct result for what is observed. Obviously the universe got on ok for billions of years before physicists evolved so it's a simplification of reality.
But that is not the same, right? I mean, if it interacted with a force and no observation was made, the wave function doesn’t collapse, does it? Honest question (to avoid any defensiveness, I should disclose that I don’t subscribe to panpsychism).
> or anything along those lines
Any suggestions?
Simple interaction between two systems doesn't cause "collapse" it makes the two systems become entangled. Classical systems are a bit contagious in this sense, anything that gets entangled with them becomes classical.
To be a bit more precise, this distinction between classical and quantum is a bit our fault. Everything is quantum at a fundamental level, classical system is one for which we do have not have a precise knowledge of the state of the system, instead we have a coarse representation. This should make more obvious in which way "classicalness" is contagious. Since the knowledge of a part was coarse, the knowledge of the newly entangled system is also necessarily coarse.
Consider the classic two-slit interference experiment. Whether the electron goes through the left or right slit can be treated a single qubit. Use a controlled-NOT gate to copy that qubit onto a second storage location, without observing either. Optionally drop the second qubit into a black hole to head off any claims about supposed future observations. Allow the electron to continue. Do you still observe interference pattens as in the non-copying version of the experiment? Why or why not?
Using the word copy in conjunction with C-NOT is slightly misleading as the copies do not behave independently.
Tongue-in-cheek explanation: Maybe whoever wrote our simulation used shallow copy when they should have done a deep copy.
That's what the word "copy" means. If you flip a coin and copy that bit, you will observe that those copies do not behave independently either. If you want independent bits, flip two coins.
Similarly, "erasing" a (qu)bit technically consists of performing a exchange operation between it and a known-zero bit. In typical electronic computers, this would generally involve diffusion-like exchanges between the voltage level in a memory capacitor (such as a FET gate) and that on the GND rail, which has a much greater effective number of bits and therefore will stay mostly zero, but eventually requires a thermodynamic expenditure of known-valued bits (aka negentropy) from some external source to maintain its voltage level / bit zeroness. (This is rather simplified; there's lots of other sources of known-zero and known-one bits getting depleted and replenished, and the exact accounting depends on how you interpret various physical states information-theoretically.)
Any two systems interacting will cause the collapse. It doesn't matter if the system is attached to a scientist or not.
> Any suggestions?
No, I'm a software developer, not a quantum physicist. :)
I suppose that means if a photon, say, is reflected by a mirror, that should collapse its wave function and any measurements after that should not have any effect on it?
Maybe it should be qualified what kind of interaction collapses wave function?
> I'm a software developer, not a quantum physicist.
Great, I’m not a quantum physicist either—yet here we are, talking about quantum physics!
I'm not sure if that example is the right one to use, but yes, that's roughly my understanding.
