In the 1930s, Einstein was displeased with quantum mechanics. He published a speculation experiment, According to this experiment, the point at which an event occurs in the universe can immediately affect another arbitrary event, He calls it “ghostly meta-range effect” and thinks it is ridiculous Because it means breaking the limitation of relativity on the speed of light for the transmission of information. But now, we have been able to complete this experiment, also found that, indeed, as ghostly. But to understand it, we must first understand what it means to be “spin.” All the basic stats have a feature called spin, they do not really spin on their own, But this metaphor is appropriate – they all have angular momentum and direction in space. Now we can measure the spin of a particle, but we have to decide which direction to measure, And there are only two solutions for measuring results: not aligned with the measured direction, called spin-up; Is opposite the measurement direction, called the measurement down. But if the direction of particle spin is vertical and we measure it horizontally? Then he will have a 50% chance of spin up; 50% chance of spin down, And after the measurement, the particle will maintain the spin result, so the measurement does change the spin of the particle.
Then if we measure the spin at a 60 degree angle to the vertical line? Then because this particle is more aligned measurement direction, it will have a 3/4 chance of spin upward; One-fourth chance of spin down, the probability of square cosine. Now an experiment like Einstein’s can be represented by two particles, But these two particles must be made in a special way, For example, two spontaneous energy generated, but because the universe’s total angular momentum must be conserved, You know that if one particle is spin-up after measurement, the other spin-off of the particle with the same measurement direction is down. I must point out that the spins of each pair must be opposite only when the measurement directions of the two particles are the same.
Now things get a bit weird: You might think that each particle is given exactly the specified spin when it is created, But this does not work – imagine the spins of these two particles being the opposite and vertical, measured horizontally, Each one has a 50/50 probability of spin up / down, so in fact there will be a 50% chance of the two measurements will get the same result, But this violates the law of conservation of angular momentum. According to quantum mechanics, these two particles are not given exactly the specified spin, They are actually intertwined, meaning that their spin is actually the opposite, So when one of the particles is measured and the spin is confirmed, you can immediately know exactly what the other particle’s measurement is, This has been rigorously tested many times in many experiments: regardless of the angle of measurement and how far apart the two particles are, The measurement results must be the opposite. Now stop and think about how crazy it is: Neither particle has an exact spin, but as soon as you measure one, you can immediately know the spin of another particle, But the two may be a few light years away.
Some theorists interpret this result as: The first measurement will affect the second measurement of the speed of light, but Einstein may not think so, He was very disturbed, he would rather believe it instead of explanation: the particles have hidden information, So that any measurement direction will have a given spin direction, just before the measurement we do not know what this information is. Now because the hidden information that two particles created when they were created was in the same place, So there’s no need for any message to be faster than the speed of light between the two particles. For some time, scientists accepted the idea that some of the particles before the measurement of unknown information, But then John Bell used a method to test the idea, This experiment can confirm whether the particles always have hidden information, the following is how it works: There are two spin detectors, each measuring the spin in one of three different directions, The measurement direction will be prepared with the choice, and independent of the other detector, Now a pair of entangled particles or sent to these two detectors, And record the same measurement results – all up / down, or different, we will continue to repeat this experiment, And to a variety of random combination of measuring direction to measure, hoping to find out the two detectors give different results probability, And this probability is to judge whether there is always the key to hide information, in order to understand the reason, Let’s figure out the theoretical odds of disparate results with hidden information, and now you can imagine the secret project of hiding information as particles of mutual recognition, Now you can imagine the secret project of hiding information as particles of mutual recognition, And the only criterion is to measure two particles in the same direction, the result must be the opposite, For example: The first is that one of the particles gives an upward spin in each measurement direction, While the other pair will give a spin down; The other is that one of the particles gives an upward spin in the first direction, a second direction gives a spin down, a third direction gives an upward spin, While its other pair gives a spin down in the first direction, the second direction gives an upward spin, the third direction gives a downward spin, Any other kind of project is mathematically equal, so we can calculate the theoretical odds by both programs.
Now I visualize the project of these particles, that is, their hidden information. In the first case, the result will obviously be 100% different and the direction of the measurement will not be important. However, different directions in the second plan will produce no result. For example, when both detectors measure the first direction, particle A will give spin up and particle B will spin down, The results are different; however, if the detector B measures in the second direction, the spin is given up and the result is the same. We can go ahead and try out all the possible combinations, and we will find that, The difference was five out of nine times, So the probability of two different plans for the 5/9, and the probability of a different program is 100% So in short, if there is really hidden information, the probability of dissimilarity should be greater than 5/9, The result of that experiment? In fact, only 50% of the odds will be different, This is not reasonable So experiments ruled out the idea of hiding information to have different outcomes in different directions.
How does quantum mechanics explain this result? Assuming the detector A is measured in the first direction and the result is spin-up, Then you can immediately know the other particle in the first direction measurement results spin down, However, only one-third of the probability of each measurement in the first direction, but the particle B measured in the other two directions, It will be measured with the direction of 60 degrees angle, As the film begins with a 3/4 chance of spin up, Since the probability of being measured by both directions is only 2/3, particle B gives a spin-up probability of 2/3 times 3/4 to 1/2, So the two detectors give the same result probability of 1/2; the difference is 1/2, just as the experimental results, So quantum mechanics is right, but how to explain these results is still controversial: Some physicists see this as proof that there is no hidden information in quantum particles, And the spin is only meaningful when the particles are measured; Other physicists believe tangled particles will update each other’s hidden messages at superluminal speeds when measured.
So does this mean that we can use tangled particles to achieve superluminal communication? Hmmm … everyone did not think it was because the results you found on both gauges were all random, Will not be different for different measurement directions. In the other detector will only get a 50/50 chance of spin up / down, Only when the operators of the two gauges compare the measurement records will find that when they choose the same direction, They all get the opposite spin, the measurement data on both sides are random, just contrary to the other random, This is indeed ghostly, but it does not allow the transmission of information between two points faster than the speed of light, It will not violate the theory of relativity, At least, will make Einstein happy..