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Nobel Prize in Physics 2022 Explained: Quantum Entanglement, Proving Einstein Wrong

The Nobel Prize for Physics in 2022 was awarded "for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science". But what does this actually mean? Around the time quantum mechanics was gaining steam as a way to describe the universe on the smallest scales, there were more and more questions cropping up about the meaning behind the theory. Although it made near-perfect mathematical predictions about what should happen in any given scenario and experiment, it went against a lot of theories that came before it (classical physics) in terms of the assumptions and implications of the theory. In classical physics, if you get enough information about a system, you can exactly predict how it should behave at a later point in time. For example, if you know a particle's position and speed at a given point in time, you can work out where to find it some time later. This prediction would also work every single time we repeated the experiment of measuring the particle's position at a later point in time. In quantum mechanics, however, we can get different experimental results for repeating the exact same experiment multiple times. And before each experiment, the only thing we can do is predict the probability of getting each possible measurement result (rather than predicting the exact result we'd get). Before the measurement, the system is in a blend, or superposition, of all possible measurement results. And upon doing a measurement, the wave function "collapses" into the single measurement result we find. All of this goes against "common sense" and also classical physics. More importantly, this goes against "determinism", the idea that everything follows a set of rules that can exactly predict the result of an experiment given enough knowledge and information about the system. Einstein, Podolsky, and Rosen (EPR) didn't like this. They used the logic employed by quantum mechanics to try and come up with a logical inconsistency. They studied the behavior (theoretically) of a pair of "quantum entangled" particles, separated by a large distance. Since the particles were entangled, making a measurement on one of them immediately also gave us information about the state of the other. But if quantum mechanics was right about the system being in a superposition before the measurement, and then collapsing right after it, then how did the second particle "know" when the measurement had been made? They reasoned that the unmeasured particle, in order to obey other laws of physics, would have to instantaneously collapse into the right state (i.e. as soon as the first particle was measured). This went against the idea known as "locality", which said that information can only be communicated between two points of space as quickly as light could travel between them. "Instantaneous" collapse, after all, did occur faster than light could travel between the particles. Therefore, they showed that the conventional interpretation of quantum mechanics broke both determinism and locality. And this was a problem because both classical physics and Einstein's theories of Relativity were heavily reliant on both principles. So EPR suggested an alternative explanation, known as a "hidden variable" theory. They suggested that hidden variables, which we would never have access to, were engrained within the particles and told the particle what state to be in at any time and position. This way, we would just "catch" the particle in a particular state when we did a measurement. In other words, the hidden variable determined (deterministically) what state the particles should be in (i.e. no random wave function collapse), and since the variable was engrained into both particles, there was no faster-than-light communication. Doing an experiment to explain the difference between these two hypotheses (hidden variable vs. quantum) was difficult, until John Bell came along and showed that correlations between results of MULTIPLE such measurements were expected to be different between the hidden variable and quantum theories. This is where our Nobel Prize winners come in. They each worked on improving Bell's theorem so it could be experimentally verified, did the experiments, closed loopholes, and further developed quantum information theories to study ideas like quantum teleportation! Thanks for watching, please do check out my links: MERCH - https://parth-gs-merch-stand.creator-... INSTAGRAM - @parthvlogs PATREON - patreon.com/parthg MUSIC CHANNEL - Parth G's Shenanigans Here are some affiliate links for things I use! Quantum Physics Book I Enjoy: https://amzn.to/3sxLlgL My Camera: https://amzn.to/2SjZzWq ND Filter: https://amzn.to/3qoGwHk www.nobelprize.org/prizes/physics/2022/summary/ wikipedia.org/wiki/EPR_paradox 0:00 - Quantum Physics Basics 6:27 - EPR Paradox 10:53 - Hidden Variables, Bell's Theorem, Nobel Prize