Some things are related, others are not. Suppose you randomly select a person from a crowd who is significantly taller than the average. In that case, there is a good chance that they will also weigh more than the average. Statistically, one quantity also contains some information about the other.
Quantum physics allows for even stronger links between different quantities: different particles or parts of an extensive quantum system can "share" a certain amount of information. There are curious theoretical predictions about this: surprisingly, the measure of this "mutual information" does not depend on the size of the system but only on its surface. This surprising result has been confirmed experimentally at the TU Wien and published in Nature Physics. Theoretical input to the experiment and its interpretation came from the Max-Planck-Institut für Quantenoptik in Garching, FU Berlin, ETH Zürich and New York University.
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