Bell's Inequality: The weirdest theorem in the world | Nobel Prize 2022

Thank you for not playing annoying music whilst we're trying to follow the explanation.👍

Understanding it is one thing but then explaining it in a simple way to ordinary people is a craft in itself. Excellent lesson.

As Einstein said, “If you can't explain it simply, you don't understand it well enough.” you have shown that you indeed understand this completely! Thank you for the simple explanation and the example for us to try.

Olivia, it is a joy to watch your presentations. I saw one from Al Khalili explaining Bells inequality, but yours has made it much clearer, which has increased my understanding of Quantum Physics to about 2%. :) Keep posting!

One thing that is interesting is how much Einstein influenced Quantum Mechanics, even if he did not agree with the philosophy behind it. The EPR paper was the end result of a series of arguments between Einstein and Bohr over the underlying meaning of QM. Einstein would present an argument against the probabilistic nature of QM, and Bohr would provide a counterargument showing Einstein where he was wrong. Eventually Einstein came up with the argument in the EPR paper that Bohr could not answer. Bell also did not answer it, but he came up with a way to, in theory, answer the question about which interpretation was correct. And then the three Nobel winning scientists came up with experimental ways to use Bell's theorem. Without the EPR paper quantum entanglement would probably never have been looked at and measured. So even when wrong Einstein made a great advance in science.

John Stewart Bell's birth town of Belfast (and, of lesser significance, my own birth town) has a street interestingly named for the theory rather than its discoverer: 'Bell's Theorem Crescent'. I discovered it accidentally on a walk around Belfast a couple of years ago and have often wondered if it existed on Google Maps prior to my observing it!

Bell did not assume "realism". In fact he pointed out himself (!) that his theorem is about models, not about reality. He instead assumed a second property called "measurement independence". This was pointed out among others (ironically) by one of the recipients of the Nobel Prize, John Clauser.

This is somewhat past my mathematical understanding but I really appreciate your taking the time to break it down so I can understand it and hence expand/bend my mind a little. At 61yo I do regret not pushing myself more in my mathematics study- just a word to the young scientists and mathematicians out there: keep grinding!!

Love how they proved quantum mechanics is real and it just leads to "we have no idea what the hell is going on"

What an excellent presenter; you can feel the respect for the material and the people involved.

It's wonderful what can result from people doing what they are truly passionate about. Paths are drawn so much cleaner and we can conclude collectively, so much more efficiently. Thank you again for another thoughtful and extremely well-presented piece, Olivia ♡

That was wonderfully clear and well presented. Excellent stuff !

It's worth pointing out why you can't build an ansible (FTL communicator) with entangled particles. When Alice interacts with her q-bit, the probability function does indeed collapse for both q-bits at the same time -- but Bob doesn't know that the probability function for his particle has collapsed. Further, when Bob does interact with his q-bit, he can't distinguish between the case "probability function has already collapsed due to Alice" and "Probability function just collapsed due to Bob's interaction". Finally, neither Alice nor Bob can influence how the probability function collapses to favor one value or the other. Thus, once Bob interacts with his q-bit he can say with certainty what value Alice will get when she interacts with her q-bit but not whether or not she has or hasn't. Since the measured value is random, no useful information has been transferred. Interestingly, entangled q-bits do have some use in communication -- they can be used to authenticate messages. In this scenario, Alice interacts with her q-bit and uses that value as part of the encryption key of a message. When Bob receives the message, he interacts with his q-bit to create the decryption key. While a single q-bit doesn't give Bob much confidence that Alice sent the message, if 256 q-bits are used...

I see lots of comments about this being a clear explanation. What am I missing then? I feel like there's a considerable amount of information missing about the experiment that is crucial to understand anything about it. A and B are sent a particle and measure x or y projection. x and y projection of what? Some vector? No idea, but I can accept that they measure some kind of quantity that, after normalization, can only be -1 or 1. Then, after many runs of that, they average out their measurements and compute (Ax + Ay)Bx + (Ax-Ay)By. I understand that the outcome of that can not be >2. But, what does that have to do with locality or realism? I don't see a connection there at all? Then you quickly move to an example with Qbits and the fact that the outcome becomes ~2.8. The conclusion is that either particle moves faster than the speed of light, or realism is incorrect. Again, Why?? What does the speed of the particles have to do with measuring -1 or 1? What does realism have to do with measuring -1 or 1? If the outcome is higher than 2, namely ~2.8, that can only happen when some measurements have not been 1 or -1, but >1 or < -1? So yeah, this feels like one of those times an explanation is simplified and information is omitted up to a point where the whole explanation makes no sense at all anymore and is basically useless. Sorry for the harsh words, but this is frustrating, haha

One of the coolest explanations of bell inequality I've seen and you literally fulfilled fenyman's idea of being able to explain the idea in the coolest possible way.

Thank you for explaining it so well! Definitely leaves us with some interesting things to explore regarding the relationship between entangled particles.

Finally, a channel that isn’t scared to show some of the maths that is so crucial to the underlying physics of this exciting news.

John Bell was a technician in Queens for some years. People realised his genius and helped him get his degree encouraged him to get his PhD. He had died before I started there but by all accounts he was a lovely bloke.

Yes I loved the fact that there was no annoying background music and Yes I agree with all others that you are an excellent presenter. If I may mention that the Nobel Prize work was not all done in a lab. I watched and loved the presentation on Nova, Eisnstein's Quantum Riddle where an experiment in the Canary Islands Observatory have done some amazing experiments.

Well done. I understand some of it; I am still learning. At 77 it is difficult to comprehend since everything I learned is now passe. The universe is joyfully weird.