"A grin without a cat" is how Lewis Carroll describes the Cheshire Cat's mysterious way of disappearing while leaving its grin behind in his 1865 classic, Alice in Wonderland. The fanciful character raises a question that has captured physicists' attention over the past few years: can an object be separated from its properties?
In 2013, Yakir Aharonov and his coauthors conceived of an experiment suggesting that a photon can be separated from its polarization (a property that tells the direction in which a wave oscillates). The following year, Tobias Denkmayr and coauthors carried out a similar experiment in which neutrons seemed to be separated from their spin (a property involving angular momentum). Aharonov's group called the effect a "quantum Cheshire Cat."
However, in a new paper published in the New Journal of Physics, Raul Corrêa, Pablo Saldanha, Marcelo Santos, and C. H. Monken from the Federal University of Minas Gerais in Belo Horizonte, Brazil, have questioned this interpretation of the results. Instead of a particle being separated from its properties, they suggest that the results can be explained by a standard quantum effect, quantum interference, in which an individual particle interferes with itself due to its wave-like properties.
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