What are hidden variables and the significance of Bell's Theorem?

In summary, the Bell's inequality states that the number of objects with certain parameters is greater than or equal to the number of objects with different parameters. However, in the quantum world, this inequality is violated due to hidden variables that cannot be observed currently. Bell's theorem shows that any theory that includes these hidden variables must also respect relativity and cannot be local, whereas quantum mechanics predicts equality.
  • #1
Ed Quanta
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I have found a site that derives Bell's inequality
The number of objects which have parameter A but not parameter B plus the number of objects which have parameter B but not parameter C is greater than or equal to the number of objects which have parameter A but not parameter C.

And I follow this derivation alright, but I have seen examples where this inequality is violated when the objects we imply this inequality to things in the quantum world like the spin of an electron for orientations of different angles. Now, what I read is that these violations are not really violations due to the fact that Bell's theory is based on the assumptions that logic is valid and that hidden variables exist locally. What are hidden variables exactly? And what is the significance of Bell's Theorem?

Note* I know this is similar to the post earlier on Bohmian mechanics but I wanted to take a step backwards for a moment before even beginning to look into Bohm's Implicate Order ideas.
 
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  • #2
A hidden variable theory is one that claims the weirdness of QM is due to neglecting some unknown factor(s), which cannot be observed at present, but which by their dynamics account for the quantum effects without breking with classical physics. Bell showed that for any such theory which also respects relativity, any local hidden variable theory, the inequality would be strict, but quantum mechanics predicts equality.
 
  • #3


Hidden variables refer to theoretical, unobservable properties or quantities that are thought to determine the behavior of a system. These variables are not directly measurable, but are believed to exist in order to explain the seemingly random behavior of particles in quantum mechanics.

Bell's Theorem, also known as Bell's Inequality, is a mathematical proof that attempts to address the long-standing debate in quantum mechanics about the existence of hidden variables. The theorem shows that if hidden variables do exist, they must violate certain inequalities, which have been experimentally confirmed to be true in quantum systems.

The significance of Bell's Theorem lies in its implications for our understanding of the fundamental nature of reality. It challenges the traditional view that particles have definite properties and behaviors, and suggests that there may be underlying factors or variables that we cannot observe or measure. This has led to the development of alternate theories, such as Bohmian mechanics, which attempt to explain the behavior of particles in a way that is consistent with Bell's Theorem.

Furthermore, Bell's Theorem has also sparked continued research and experimentation in the field of quantum mechanics, as scientists seek to further understand and test the implications of the theorem. It has also played a crucial role in the development of quantum computing and other technologies that rely on the principles of quantum mechanics.

In summary, Bell's Theorem highlights the limitations of our current understanding of the quantum world and challenges us to question our assumptions about the nature of reality. It continues to be a topic of interest and debate in the scientific community, and has opened up new avenues for exploration and discovery in the field of quantum mechanics.
 

1. What is Bell's Theorem?

Bell's Theorem is a mathematical proof in quantum mechanics that challenges the classical understanding of the physical world. It states that no physical theory based on local hidden variables can reproduce all of the predictions of quantum mechanics.

2. Why is Bell's Theorem important?

Bell's Theorem has significant implications for our understanding of the fundamental nature of reality. It suggests that there are inherent limitations to how much we can know about the physical world, and that there may be non-local connections between particles that cannot be explained by classical physics.

3. How does Bell's Theorem relate to Einstein's theory of relativity?

Bell's Theorem challenges the concept of local realism, which is a key principle in Einstein's theory of relativity. It suggests that there may be connections between particles that are not limited by the speed of light, which goes against the principles of relativity.

4. What are some practical applications of Bell's Theorem?

Bell's Theorem has been used to develop quantum cryptography, which is a method of secure communication that relies on the principles of quantum mechanics. It has also been used in quantum computing, which has the potential to greatly increase processing power and solve complex problems in fields such as chemistry and finance.

5. How is Bell's Theorem tested and verified?

Bell's Theorem has been tested through various experiments, such as the Bell test experiments. These experiments involve measuring the correlations between the properties of entangled particles and comparing them to the predictions of classical physics and quantum mechanics. So far, the results have consistently supported the predictions of quantum mechanics, providing evidence for the validity of Bell's Theorem.

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