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  • Albert Einstein played a key role in launching quantum mechanics to his theory of photoelectric effect.

  • But remains deeply bothered by its philosophical implications.

  • And though most of us still still remember him for deriving e equal m c square.

  • His last contribution to physics was actually a 1935 paper.

  • Co-author with his young colleague - Boris Podolsky and Nathan Rosen.

  • Regarded as an art philosophical foot note well into the 1980s.

  • This EPR paper has recently become central to a new understanding of quantum physics.

  • With its description of a strange phenomenon now known as entangled states.

  • The paper begins by considering a source that splits out the pair of particles

  • Each with two measurable properties.

  • Each of these measurements has two possible results of equal probability.

  • Let’s say zero or one for the first probability and A or B for the second.

  • Once a measurements is performed, subsequent measurement of the same properties in the same particle will yelled the same result.

  • The strange application of this scenario is not only the state of the single particle

  • Is indeterminate until it’s measured.

  • But that the measurement then determine the state

  • What’s more the measurements affect each others.

  • If you measure a particle as being in state one and followed it up with the second type of measurement

  • Youll have a fifty percent chance of getting either A or B.

  • But if you then repeat the first measurement,

  • Youll have a fifty percent chance of getting zero

  • Even that the particle have already been measured one.

  • So switching the properties been measured scramble the original results.

  • Allowing for a new random value.

  • Things get even stranger when you look at both particles.

  • Each of the particle will produce random results, but if you compare the two

  • Youll find that theyre always perfect league correlated.

  • For example, if both particle are measured at zero.

  • The relationship will always hold.

  • The states of the two are entangled.

  • Measuring one will tell you the other with absolute certainty.

  • But this entanglement seems to defy Einstein’s famous theory of relativity

  • Because there is nothing to limit the distance between particles.

  • If you measure one in New York at noon, and the other in San Fransinco and then the second later

  • They still give the exactly same result.

  • But if the measurement does the terminate value then this will require one particle sending some sort of signal to the other

  • At thirteen million time the speed of light which according to relativity is impossible.

  • For this reason, Einstein dismiss entanglement asspuckhafte ferwirklung

  • Orspooky action at a distance

  • He decided that the quantum mechanics must be incomplete a mere approximation of a deeper reality.

  • In which all particles have pre-determine states that are hidden from us.

  • So porter of orthodox quantum theory led by Neil Bohr maintain that quantum state really are fundamentally indeterminate

  • And entanglement allows the states of one particle to depend on that the distance partner

  • For thirty years, physics remained at in past until John Bell

  • Figured it out that the key to testing the EPR argument was to look in cases involving different measurements on the two particles

  • The local hidden variable theories favored by Einstein Podolsky and Rosen

  • Strictly limited how often you can get results like 1A or B0

  • Because the outcome would have to be defined in advance

  • Bell showed that the purely quantum approach where the state is truly indeterminate until measured has different limits

  • And predicts measurement results that are impossible in the pre-determine scenario

  • Once Bell had worked out how to test the EPR argument physicists went out and did it.

  • Beginning with John Clauster in the seventies and Alain Aspect in the early 80s

  • Dozens of experiments has tested the EPR prediction and all have found the same thing

  • Quantum mechanics is correct.

  • The correlations between the indeterminate states of entangle particles are real

  • And cannot be explained by any deeper variable

  • The EPR paper turned out to be wrong but brilliantly sell

  • By leading physicists to think deeply about the foundations of quantum physics

  • It led to further elaborations of the theory and help launch research into subjects like quantum information

  • Now a thriving field with the potential to develop computers of unparallel power

  • Unfortunately, the random of measure results prevent science fiction scenario like using entangle particles

  • To send messages faster than light.

  • So relativities is save for now but the quantum universe is far stranger than Einstein wanted to believe

Albert Einstein played a key role in launching quantum mechanics to his theory of photoelectric effect.

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B2 US TED-Ed quantum particle measurement einstein measured

【TED-Ed】Einstein's brilliant mistake: Entangled states - Chad Orzel

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    Go Tutor posted on 2014/11/17
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