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Quantum Superposition - Both Exists And Does Not Exist

 

One of the strangest things about quantum physics is that it is in a superposition state. In fact, we are not so unfamiliar with this concept in our daily lives. When we look at it classically, if we consider ropes as an example, it is an example of classical superposition that two ropes show the feature of a single rope by overlapping the waves that will form.

However, as with everything else, the superposition meaning of quantum is different. Here we need to think differently from the classical analogy. Because the owners of the quantum world are atoms and subatomic particles. Let us consider the most commonly used electrons experimentally. Electrons have a phenomenon we call spin.

What is Spin?

Spin, as the name suggests, is rotation. However, I would like to clear up the misunderstanding here. Electrons or particles are not round, ball-like structures as we imagine. In order to explain them in a mathematically understandable way, we give them spin property, in other words, we can say that particles have an intrinsic property.

The concept of spin becomes very important in experiments. Thanks to them, we can reach the information of electrons or particles in the most general form. As we mentioned in our previous article, particles have an information box, that is, wave functions. These wave functions carry information over probabilities. When we precipitate the wave functions, that is, when we make a measurement, we get a clear result about the spin of the electron in our example.

Let's prepare an imaginary experimental setup:

The first step is to prepare a physical system.

For example, we want to prepare the direction of the spin of an electron to be up. We have to put the electron in the magnetic field. Until we measure with detectors, the spin of the electron we have is in both an up or down state within the possibilities, that is, it is in a superposition state.

 
     Experimental spin measurement setup.

As soon as we measure, we learn whether the spin is up or down. The way to understand this experimentally is very simple. If the detector we put at the end of the measuring setup caught a photon, our particle was standing in the opposite direction to the magnetic field in it, and it emitted a photon while passing to the minimum energy level (changing its spin direction). On the other hand, if our detector did not capture any photons, it did not emit any photons because the spin of our electron is in the same direction as the magnetic field it is in. So, if we want to get a spin with an upward direction, we have to set up an arrangement with the magnetic field upwards. In this way, our measurement result is consistent with our estimates.

The most basic situations that I have explained above are that the particles have an even weirder phenomenon called entanglement in the next stages. Entanglement is the most important indicator of superposition. Until two entangled particles do not measure, they have all possible probabilistic information simultaneously. Whenever we measure one of the samples, we can have instant information (they interact at the speed of light) on the other. I will explain this in detail in another article. 

Stay curious. :)

 

 

Reference

https://scienceexchange.caltech.edu/topics/quantum-science-explained/quantum-superposition

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