Comment on observer đ observed quantum state
pcalau12i@lemmygrad.ml â¨1⊠â¨day⊠agoQuantum mechanics is not complicated. It just appears complicated because everyone chooses to interpret it in a way that is inherently contradictory. One of the fundamental postulates of quantum mechanics is that it is time-symmetric, called unitarity, but almost everyone for some reason assumes it is time-asymmetric. This contradiction leads them to have to compartmentalize this contradiction in their head, which then leads to a bunch of a contradictory conclusions, and then they invent a bunch of nonsense to try and make sense of those contradictions, like collapsing wave functions, a multiverse, cats that are both dead and alive simultaneously, particles in two places at once, nonlocality, etc. But thatâs all entirely unnecessary if you just consistently interpret the theory as time-symmetric. This has been shown in the literature for decades, called the Two-State Vector Formalism, yet itâs almost entirely ignored in the popular discourse for some reason.
stephen01king@lemmy.zip â¨20⊠â¨hours⊠ago
How does that explain photons acting like a wave or a particle depending on whether they were observed or not in the double slit experiment?
pcalau12i@lemmygrad.ml â¨14⊠â¨hours⊠ago
Well, first, that is not something that actually happens in the real world but is a misunderstanding. Particles diffract like a wave from a slit due to the uncertainty principle, because their position is confined to the narrow slit so their momentum must probabilistically spread out. If you have two slits where they have a probability of entering one slit or the other, then you will have two probabilistic diffraction trajectories propagating from each slit which will overlap with each other.
Measuring the slit the photon passes through does not make it behave like a particle. Its probabilistic trajectory still diffracts out of both slits, and you will still get a smeared out diffraction pattern like a wave. The diagrams that show two neat clean separated blobs has never been observed in real life and is just a myth. The only difference that occurs between whether or not youâre making a measurement is whether or not the two diffraction trajectories interfere with one another or not, and that interference gives you the black bands.
This is an interference-based experiment. Interference-based phenomena can all be given entirely classical explanations without even resorting to anything nonclassical. The paper âWhy interference phenomena do not capture the essence of quantum theoryâ is a good discussion on this. There is also a presentation on it here.
Basically, you (1) treat particles as values that propagate in a field. Not waves that propagate through a field, just values in a field like any classical field theory. Classical fields are indeed something that can take multiple paths simultaneously. (2) We assume that the particles really do have well-defined values for all of their observables at once, even if the uncertainty principle disallows us from knowing them all simultaneously. We can mathematically prove from that assumption that it would impossible to construct a measuring device that simply passively measures a system, it will always perturb the values it is not measuring in an unpredictable way.
A classical field has values everywhere. Thatâs basically what a field is, you assign a value, in this case a vector, to every point in space and time. The vector holds the properties of the particles. For example, the X, Y, and Z observable would be stored in a vector [X, Y, Z] with a vector value at any point. What the measuring device measures is |0> or |1>, where we interpret the former to meaning no photon is there and we interpret the latter to mean a photon is there. But if you know anything about quantum information science, you know that |0> just means Z=+1 and |1> just means Z=-1. Hence, if you measure |0>, it doesnât tell you anything about the X and Y values, which we would assume are also there if particles are excitations in a field as given by assumption #1 because the field exists everywhere, and in fact, from our other assumption #2, your measurement of its Z value to be |0> must perturb those X and Y values.
It would be the field that propagates information through both slits and the presence of the measurement device perturbs the observables you do not measure, causing them to become out of phase with one another so they that they do not interfere when the field values overlap.