For "experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science," the Nobel Prize in physics was given this year.
We need to understand how these experiments resolved a protracted argument among physicists in order to comprehend what this means and why this work is significant. John Bell, an Irish physicist, was a significant participant in that discussion.
In the 1960s, Bell made the connection between what we know about the world and how the world actually is by figuring out how to translate a philosophical inquiry about the nature of reality into a physical question that could be addressed by science.
Entangled quantum states
We are aware that quantum items possess qualities we don't typically attribute to everyday objects. Light alternates between being a wave and a particle. This never happens with our refrigerator.
There are two main categories of explanations we might consider when seeking to explain this uncommon behaviour. One alternative is that we see the quantum world exactly as it is, and it just so happens to be strange, and we perceive it that way. Another alternative is that the quantum world is exactly like the familiar, beloved world, but our perception of it is corrupted, making it impossible for us to see quantum reality as it actually is.
There was disagreement among physicists over which explanation was correct in the first half of the 20th century. People like Werner Heisenberg and Niels Bohr were among those who believed that the quantum world is simply odd. Albert Einstein and Erwin Schrödinger were among those who believed that the quantum world must be just like the conventional world and that our perception of it is only hazy.
This divide is based on a peculiar quantum theory prediction. The theory states that even when two interdependent quantum systems are separated by a vast distance, their properties continue to be dependent on one another.
Schrödinger invented the word "entanglement" for this occurrence in 1935, the same year he came up with his famous thought experiment featuring a cat trapped in a box. He claimed that it is foolish to think the world operates in this manner.
Entanglement's drawback
It would appear that entangled quantum systems are instantly communicating with one another if they truly remain coupled even though they are separated by great distances. However, the theory of relativity developed by Albert Einstein prohibits this kind of relationship. This concept was dubbed "spooky activity at a distance" by Einstein.
Once more in 1935, Einstein and two colleagues came up with a thought experiment that demonstrated that entanglement cannot be fully explained by quantum physics. They reasoned that there must be more to the world than what we can now perceive.
But as time went on, the issue of how to interpret quantum theory faded into obscurity. The issue appeared too abstract, and in the 1940s, many of the top quantum physicists were hard at work applying the theory to a very real project: developing the atomic bomb.
The scientific community didn't understand this seemingly abstract query could have a concrete solution until the 1960s, when Irish physicist John Bell focused on the issue of entanglement.
The Bell Theorem
Bell expanded Einstein's 1935 thought experiment by using a straightforward entangled system. He demonstrated that the quantum description could not be incomplete while still forbidding "spooky action at a distance" and complying with quantum theory's predictions.
It feels like bad news for Einstein. However, this did not give his opponents an automatic victory.
This is due to the fact that it was unclear in the 1960s whether or not the predictions of quantum theory were accurate. Someone needed to do an experimental test of this real physical system that had been converted into a philosophical argument about reality in order to truly demonstrate Bell's claim.
Naturally, this is where two of this year's Nobel laureates join the narrative. The experiments on Bell's suggested system, first carried out by John Clauser and then by Alain Aspect, finally demonstrated the veracity of quantum mechanics' predictions. There is no other description of entangled quantum systems that can explain the observed quantum world, unless we accept "spooky action at a distance."
So Einstein was mistaken?
Perhaps as a surprise, but it appears that Einstein was mistaken about this due to recent developments in quantum theory. In other words, it appears that we do not have a hazy understanding of a quantum world that is identical to our regular one.
The notion that we can clearly see a quantum world that is exceptional by nature, however, is oversimplified. And this reveals one of the most important philosophical truths of this quantum physics episode.
Beyond our scientific description of the quantum world, or beyond the knowledge we currently possess, it is no longer obvious that we can rationally discuss it.
According to Anton Zeilinger, the third-place Nobel laureate for this year: "It is impossible to distinguish between reality and our knowledge of reality or between information and reality. It is impossible to refer to reality without using the knowledge we now possess about it."
This distinction, which we frequently believe to be the foundation of our everyday perception of the world, is now irretrievably muddled. John Bell is to be credited for this.
Source: The Conversation
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