The process that Alice is experiencing here, is precisely what we are trying to teach children in school. We know what two apples are and we know what the two pears are. But what is 'two' without anything attached? Does the number two exist in reality, or does it exist only in my head? That is exactly the same philosophical question that Alice is wondering about. The cat's grin - in what sense does it exist independently of the cat?

But the Cheshire Cat that is seperated from its grin is not only a mathematical idea. It is a physical reality, too. Recently, scientists observed the existens of a 'quantum Cheshire Cat': if a quantum system is subject to a certain pre- and postselection, it can behave as if a particle and its property are spatially separated. The scientists report an experiment in which they send neutrons through a perfect ​silicon crystal interferometer and perform weak measurements to probe the location of the particle and its magnetic moment. The experimental results suggest that the system behaves as if the neutrons go through one beam path, while their magnetic moment travels along the other.