The 2022 Nobel Prize in Physics was finally announced on October 4, 2022 by Alan Aspe from France, John Crowser from the United States, and Salinger from Austria, recognizing these three physicists who determined that the Bell inequality was not valid through photon entanglement experiments and pioneered the field of quantum information science.
In a way, the result of the award is directly on a larger communication surface to let us know that Einstein is wrong, why?
Because the Nobel Prize was awarded to the quantum entanglement experiment that confirmed that Bell's inequality did not hold, and this experiment directly rejected Einstein's idea that the quantum world still maintains localized reality.
EPR paradox
Back in 1935, Einstein and two of his assistants, Podolsky and Rosen, published an article titled "Can Consider the Description of Physical Reality Complete by Quantum Mechanics?" " paper.
We will not talk much about the content of the paper, but its core idea is called the EPR paradox, which can be understood in general through the following example:
Imagine a pair of entangled particles, if you separate the two tens of thousands of light-years apart, when we measure one of them, for example, particle A spin measurement is up, because the two are entangled, then the distant B particle is naturally spin downward.
First of all, the Copenhagen interpretation holds that before measuring the A particle, it is in a superposition of both upward and downward spin, and once the measurement behavior is generated, the wave function collapses, and the only measurement result will be obtained, either up or down, and the B particle in the distance also detaches from the superposition state at that moment and becomes the opposite of the spin of the A particle.
Einstein believed that there was a loophole in this process, first of all, it did not recognize that the spin state of the particle needs to be measured to be known, because this is not in line with physical reality, the state of the particle should be prepared from the beginning is determined, like the moon in the sky, when you do not look at it, it does not exist?
Secondly, since the spin state has long been determined, no matter how far apart the AB is, as long as one of the particle states is measured, then the state of the other particle is naturally known, as if you open a pair of sets into two boxes, one box left on Earth, the other box on Mars, and now the other person only needs to open the Earth box to immediately know whether the Mars box contains a glove or a right glove.
In the Copenhagen interpretation, the state of the first two particles measured is uncertain, both are in a superposition state, and only the moment when one of the particles is measured, the other particle determines its state. Einstein argued that this process violated the requirement of locality, that is, there was a faster-than-light information connection between AB particles, which Einstein himself called "ghostly over-range."
- Hidden variable theory
Of course, Einstein's view must have been refuted by the Copenhagen School, and its boss Bohr was naturally the first to stand out, after all, Bohr and Einstein have always been at odds on this issue.
Bohr argues that quantum phenomena are indistinguishable, that even if AB particles are far apart, they are still a whole, that the measurement behavior causes the wave function to collapse, which naturally affects the AB particle at the same time, and that a physical phenomenon can only be called a phenomenon after measurement, and you cannot and cannot know its state until then.
But in any case, Einstein still firmly believed in the incompleteness of quantum mechanics, believing that there should be a more perfect theory on top of quantum mechanics, called the theory of hidden variables, which can eliminate those random uncertainties and then re-enable "God no longer rolls the dice."
Bell inequality
After all, physics is essentially an experimental discipline, and what can be done to prove their point?
In 1964, the British scientist John Stuart Bell proposed a famous mathematical inequality called the Bell inequality in order to support the theory of hidden variables, and opened the door to the feasibility of the EPR paradox experiment.
This inequality is a limitation of the measurement of separated particles from the perspective of classical physics, in simple terms, if the experimental results violate the Bell inequality, then the localization reality is self-defeating, and Einstein is wrong.
In order to give you a general understanding of this Bell inequality, the following is a very simple way of deriving the following process:
Build a three-dimensional rectangular coordinate system, which has 8 gua limits
Then the spin situation of the particle can be included, such as the first particle A spin direction of the split out is in the first gua limit, then from the XYZ three-axis observation, Ax is +, Ay is +, Az is +, at this time the spin direction of the B particle is obviously the opposite of A, then Bx, By, Bz are all -, and so on, when the A spin direction is in different gua limits, there will be the next seven cases with B particles, as shown in the figure
Although it is not known which result the two particles will be, the probability of these 8 cases combined is 1, but when measuring, because there are three directions to choose from, the degree of correlation of the spin state of the particle can be expressed as Pxy, Pzy, Pxz, where Pxy refers to the measurement of A particles from the X direction, the B particle is measured in the y direction, if the measurement results are consistent, then it is positive, the inconsistency is negative, and the equation is written down This is how Pxy = -N1-N2 + N3-N4 + N5-N6 + N7+ N8, and so on can write Pzy, Pxz.
Then we subtract Pxz and Pzy by absolute values, recalling the absolute value inequality || we learned in school a|-|b|| ≤|a| + |b |, so we can write it, at this time we find that these four items can become bloated, and accidentally find that the front is exactly the sum of the 8 gua limit probabilities is 1, and the back is exactly Pxy
So there is this inequality, which is the Bell inequality
The above derivation process is completely based on classical physics, that is, the results obtained by satisfying the localized reality, if the experimental results can verify that this inequality is true, it means that there is indeed a theory of hidden variables in this world, but it backfires, originally Bell wanted to prove the incompleteness of quantum mechanics, but unexpectedly consolidated the correctness of quantum mechanics.
This is somewhat similar to the story that Poisson used the theory to calculate the "Poisson bright spot" in order to oppose the wave theory of light.
summary
Therefore, in general, although these experiments and technologies that have won the prize have been realized for many years, the promulgation of the Nobel Prize in Physics is not only an affirmation of these physicists, but also a higher communication surface, so that the public has a hearing about quantum mechanics.
The first photo of quantum entanglement
There is also Einstein, the founder of the theory of relativity and the father of quantum theory, who also negated some of his ideas and beliefs about the quantum world, and it seems that he is indeed wrong.