Quantum Nonlocality

Quantum physics tells us that some tiny particles, like electrons or photons, can be connected in a special way, even when they are very far apart. This is called quantum entanglement. It means that if you measure one of the entangled particles, you can instantly know something about the other one, without having to look at it or communicate with it. This is called quantum nonlocality.

How is that possible? How can they know what each other are doing without talking?

That’s a very good question, and one that puzzled many scientists for a long time. Some of them, like Albert Einstein, thought that this was impossible, and that there must be some hidden information or mechanism that explains how the particles communicate. He called this “spooky action at a distance”.

He just meant that it was mysterious and unexplained. But later, other scientists, like John Bell and Alain Aspect, showed that there is no hidden information or mechanism that can explain quantum nonlocality. They did this by performing experiments that tested the predictions of quantum physics against those of a local realistic theory.

What is a local realistic theory?

A local realistic theory is one that assumes two things: first, that the properties of physical objects are determined before they are measured, and second, that physical effects cannot travel faster than the speed of light. These are very reasonable assumptions, and they work well for most situations in our everyday life.

They found out that the results of their experiments matched the predictions of quantum physics, and contradicted those of a local realistic theory. This means that quantum physics is not local or realistic, but nonlocal and probabilistic.

Wow, that’s amazing! So quantum physics is true?

 Well, yes, as far as we know. Quantum physics is the best theory we have to describe the behavior of the smallest things in nature. It has been tested and confirmed by many experiments over the years. But it also raises many questions and challenges about the nature of reality and our understanding of it.

Like how to interpret the meaning of quantum nonlocality. Does it imply that there is some deeper level of reality beyond space and time? Does it imply that there are multiple realities or parallel universes? Does it imply that we have free will or not? These are some of the questions that many physicists and philosophers are still debating and exploring.