Certain things are related to some extent, while others do not. For instance, if a person is randomly selected from a group and happens to be significantly taller than the average, there is a high likelihood they will also weigh more than average. In other words, one quantity can contain information about another.
With quantum physics, the connections between different quantities can be even more robust, where particles or parts of a quantum system can share information. Interestingly, the measurement of this information does not depend on the system size but only on its surface.
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