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> The fact that we observe interference patterns shows that the wavefunctions are real. well, not quite - remember that what we actually observe for a given pa
by platz 7y ago
> The fact that we observe interference patterns shows that the wavefunctions are real.
well, not quite - remember that what we actually observe for a given particular event is something that looks like particle that is localized in space.
If you're referring to the double slit experiment, the interference pattern emerges as a property of the whole collection of individual photon strikes. Yes, you need to use the wavefunction to calculate where the photon is likely to land, but each individual photon strike appears to us on the target as a single localized photon.
Whether wavefunctions are "real" is a tricky question, but just the presence in interference patterns doesn't get us to answer that question yet.
- gizmo686 7y agoIf we put the sensor in the slits themselves, what we would observe is individual photons passing through one slit or the other. What the double slit experiment shows is that there is still something of a wavefunction (whatever that actually is) at the moment the photons pass the slit, because that is how we get the interference pattern. As before when we observe the photons, we see them as single discreet particles. However, in principle this seems to be the same situation as when we detect photons passing through a slit.
- platz 7y agoRight, but in that case we never observe the wavefunction, the quantum state of the particle, or the particle interacting with itself. In that sense, the wavefunction predicts the outcome but it does not have to "real". It is real in Pilot Wave theory, but it could simply be a mathematical or calculational tool . In either case, you are right that one has to use it get the right result. Let me ask you a similar question. Are virtual particles, as described with Feynman diagrams, real?
- gizmo686 7y agoI think virtual particles are a different question, as it is at least clear what is being asked (I think they are real, but have seen no convincing arguement one way or the other). With wavefunctions, I am not actually clear on what the object "wavefunction" is. If you are asking if I believe the wave exists independent of the particle, then no. But I also do not think it is merely a calculation tool. My view is that it is analogous to "velocity" in classical mechanics. In that it is a property of the object in question. I do not know if that qualifies as "real" or not.
- zwkrt 7y agoNon-physicist perspective, if I’m out of line, please say so. It seems silly to expect that the wavefunctuon is “real” just like it is silly to assume that the gravitational field is “real” or inches are “real”. They are mathematical constructions we use to make predictions about what we see. Just because the predictions are good doesn’t make the mathematical formalism real. As a contrived example, imagine an advanced AI program running on Linux. The AI develops all sorts of models and makes very accurate predictions about what will happen in user space when it calls fopen or pipes data from /dev/urandom. But no matter how well it models the output of /dev/urandom, it will never know that the reason why the data seems random is because the kernel is generating it from a camera pointed at a lava lamp. Even if the AI was smart enough to invent models for the lava lamp and the camera optics, etc, this model wouldn’t be real, it’s still some bits in memory /describing/ what is going on outside of the AIs immediate experience.
- platz 7y agoI think this is the view that scientists if they are interested more in the task of prediction than anything else https://www.youtube.com/watch?v=ka9KGqr5Wtw https://www.youtube.com/watch?v=ka9KGqr5Wtw
- jeremyjh 7y agoNo, in a particle model there could be no interference pattern. That is the whole point. You can do the experiment - and it has been done - with a single photon and you still get interference.
- platz 7y agoYou've misunderstood my point.
- jeremyjh 7y agoMaybe so, but this sentence: "interference pattern emerges as a property of the whole collection of individual photon strikes." Is incorrect and seems to miss the whole point of the experiment. We don't need a "whole collection" to get interference, we can see it with one photon. If that doesn't mean the wave function is real, how else can it be explained?
- platz 7y agoThere is both the "interference pattern" on the target wall made by individual photons over time, which we can directly observe, and the interference of the photon's wavefunction with itself, which we cannot directly observe. I was referring to the former. We know the photon interferes with itself, via the wavefunction as you describe, but this interaction is entirely unobservable and invisible to us, and in that sense, we don't understand the ontological status of the wavefunction and what it's physical status is.
- jeremyjh 7y agoSorry, what is it we cannot observe in the latter? We see the pattern on the screen. Do you mean we cannot observe the interference that leads to that pattern? That is quite right since the only way to see a photon is to bounce it off of something.