Does quantum tunneling itself result in the collapse of the quantum object's wave function? So, as a hypothetical scenario, suppose you have a two-slit experiment, but instead of two slits, you have two slit-sized barriers that photons have some small probability of tunneling across. Would you get the interefence bands that you get with two slits, or would you get one band for each of the two barriers? Getting interference bands would mean, I believe, that tunneling does not itself result in the collapse of the wave function.
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$\begingroup$ Indeed the barriers don't make the wave function collapse. $\endgroup$– AndreaCommented Apr 28, 2022 at 20:24
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Quantum tunneling does not cause wavefunction collapse. You can usually model it as a source of a reflected wave and a transmitted wave with their respective coefficients just as in classic wave theory (optics, acoustics …). This means the transmitted wave can produce interferences.
For your thought experience, you would therefore get interference bands that depend on the transmission coefficient of the two barriers. This will typically distort the interference pattern you would get without these barriers, and lower its intensity due to reflection.
Hope this helps, and tell me if you need more details.
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$\begingroup$ Yes, that helps. Interesting. So if we have a barrier and then a screen, and we're looking at the wave function of a photon that hits the screen at time t, is there a non-zero probability that the photon will hit the barrier (not the screen) right up until time t? $\endgroup$ Commented Apr 29, 2022 at 2:00
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$\begingroup$ I’m a bit confused with your terminology. The wave function doesn’t hit the screen, it gives you information on the state of your particle. Yes, it will typically be non $0$ at the screen after some time. If you measure the particle’s position at time $t$ you will also have a certain probability to be at the barrier, but if its sufficiently long, it will have either been transmitted or reflected, the proportions being regulated by the relevant coefficients. $\endgroup$– LPZCommented Apr 29, 2022 at 7:19
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$\begingroup$ Sorry, my question wasn't clear. Let's try this. Suppose that we have a detection screen (Screen 1) the photon will activate if it reflects back; and that if it does activate Screen 1, it does so on average at t1. Suppose that we have another screen (Screen 2, at a distance on the other side) the photon will activate if it tunnels through the barrier; and that if the photon does actiavte Screen 2, it does so on average at t2, which is twice t1. If our clock reaches 99.9999% of t2 and neither screen has been activated, is there still a probability > 0 that the photon will activate Screen 1? $\endgroup$ Commented May 3, 2022 at 14:17
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$\begingroup$ PS: Without asserting definitive metaphysical conclusions, what I'm trying to get at is something like this: is it ever possible to know, prior to detection, that the tunneling has already occurred? If not, then it seems that, on one interpretation, the tunneling has not occurred until detection occurs. $\endgroup$ Commented May 3, 2022 at 14:17
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$\begingroup$ I think you are unknowingly stumbling upon the quantum eraser experiment. Do you know about it? Essentially, a prior measurement of which of the wavefunction destroys the interference pattern. $\endgroup$– LPZCommented May 4, 2022 at 8:06