Quantum Physics for Beginners: Discover the Science of Quantum Mechanics and Learn the Basic Concepts from Interference to Entanglement by Analyzing the Most Famous Quantum Experiments by Daniel Golding

Author:Daniel Golding [Golding, Daniel]
Language: eng
Format: azw3, epub
Published: 2020-08-15T16:00:00+00:00

​ Twin brothers

We said that we reveal the electron "right after" that passed through the first hole. "Right after" means that very little time has passed since it passed through the hole. But however small the time elapsed, the electron has already passed through the hole; moreover, until now it has remained a wave because we have not yet revealed it. Therefore, in the meantime, the wave has already crossed the other hole and passed through it. Isn't that right? Then how can the electron be revealed "in one piece" near the first hole? What happens to the wave that just went through the second hole? Does it disappear into thin air? It seems so, but how is that possible?

To clarify this point, the physicist Wheeler used photons and not electrons (we know by now that the result does not change) and proposed to let the photon pass through both holes, like a wave. In what way? Very simple: by inserting a detector not too far from the first hole, but not too close, in short, just enough to make sure that in the meantime the whole wavefront had already passed through the holes. In practice, you wanted to observe the photon as a particle, certainly after it had passed through both holes like a wave. The experiment was called "Delayed Choice" for this reason.

Don't worry, if we try to do it again, the result won't change. The wave disappears into thin air, as the photon is revealed as a "whole" particle, without any doubt. Yet the wave has certainly passed through the second hole too: if you don't insert the detector, the interference figure is formed (which can be formed only if the wave passes through both holes). So how is this possible?! We can only conclude that the information of the photon "caught on the fact" was immediately transmitted to the wave passing through the other hole and it disappeared.

In short, electrons, photons, and all particles exchange information in real-time, more than the "very slow" speed of light.

That's not really the case, but the example is very good. The reality is that once again we are trying to provide an objective image of what is happening. Unfortunately, we have to convince ourselves that an objective image is not adequate for reality. There is no point in saying that "the wave has already passed,” because only when we measure it can we say that something has happened. Before the measurement, the photon remains in an indefinite state of potentiality or non-objectivity (or, better still, unreality).

​ Back in time

When we then insert the detector, then we can say with certainty that the photon has passed only through the first hole and not through the second hole, and in fact, there is no interference. If instead, we do not insert the detector and we wait to see the photons only when they arrive on the target (with the relative interference figure), then we can say that each photon has made interference

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