Therefore, the following mainstream views are derived: 1. Copenhagen School: Before the observation, the electron unfolded according to the wave function (it didn't become a cloud, it was only a mathematical description), and it interfered. Once we observe it, the wave function collapses, so we can only observe the electron passing through one of the slits, not the superposition state before observation. However, further discussion of this statement will put the observer in a position beyond nature and even encounter the interference of "consciousness". Obviously, we infer from this that if we don't observe the world, then everything is meaningless, just the dispersion of wave function. This is unacceptable to anyone who has been educated in materialist philosophy.

2。 Multi-world explanation: Comrades in Copenhagen were confused by the collapse, so scientists put forward the hypothesis that the superposition state is actually a vector in Hilbert space, and thus came to the following explanation: the low-dimensional Hilbert space is not orthogonal, so the coordinate axes have projections on each other, which leads to the superposition state of events. But a little observation and intervention will inevitably make it a whole complex system, thus reaching a very high-dimensional hope space. In the case of high dimensions, the possibility of orthogonality is so great that our results are not superimposed. Generally speaking, when there are multiple possibilities with a certain probability in quantum mechanics, the universe is bifurcated, and every possibility of a result exists, but it exists in different universes and overlaps under certain circumstances. Take the above electron interference experiment as an example, that is, the electron is in a universe before reaching the double slit, but when it passes through the double slit, the universe bifurcates. Electrons in one universe pass through the A seam with a probability of 100%, and the other passes through the B seam with a probability of 100%! ?

3。 Decoherence historical interpretation: our description of historical events can be described by a density matrix. Only when our measurement target reaches a certain roughness, the matrix can be decohered, that is, the sum of probabilities on off-diagonal lines almost cancels each other, so we get a linear superposition. And if the goal we measure is too detailed, then we can't get a meaningful solution.

4。 Principle of spontaneous localization: your particle actually fills the whole universe, but in the present position, it happens to be a sharp bell curve formed by spontaneous localization of your particle, so we see where you are sitting now. You must be surprised to hear the above statement? In fact, this is a natural corollary of this theory. This theory holds that particles are actually spontaneously localized (that is, they show the state of measurement), and this representation is completely random. When the number of particles reaches a certain level, this localization is extremely common and will continue to expand (just like dominoes), so any uncertainty and superposition state can be strangely explained by this theory. But unfortunately, many experiments are challenging this theory now. /