What actually happens is much weirder, and may help us understand more about quantum mechanics.
The quantum Cheshire cat effect draws its name from the fictional Cheshire Cat in the Alice in Wonderland story. That cat was able to disappear, leaving only its grin behind. Similarly, in a 2013 paper, researchers claimed quantum particles are able to separate from their properties, with the properties traveling along paths the particle cannot. They named this the quantum Cheshire cat effect. Researchers since have claimed to extend this further, swapping disembodied properties between particles, disembodying multiple properties simultaneously, and even “separating the wave-particle duality” of a particle.
Contextuality in Quantum Mechanics
However, recent research, published recently in the New Journal of Physics, shows that these experiments don’t actually show particles splitting from their properties, but instead display another counterintuitive feature of quantum mechanics — contextuality.
Quantum mechanics is the study of the behavior of light and matter at the atomic and subatomic scale. By its nature, quantum mechanics is counterintuitive. The research team set out to fundamentally understand this counterintuitive nature, while exploring practical benefits.
“Most people know that quantum mechanics is weird, but identifying what causes this weirdness is still an active area of research. It has been slowly formalized into a notion called contextuality — that quantum systems change depending on what measurements you do on them,” said Jonte Hance, a research fellow at Hiroshima University and the
A sequence of measurements on a quantum system will produce different results depending on the order in which the measurements are done. For instance, if we measure where a particle is, and then how fast it is traveling, this will give different results to first measuring how fast it travels, and then where it is. Because of this contextuality, quantum systems can be measured as having properties that we would expect to be mutually incompatible.
“However, we still don’t really understand what causes this, so this is what we wanted to investigate, using the paradoxical quantum Cheshire cat scenario as a testbed,” said Hance.
Redefining the Quantum Cheshire Cat
The team notes that the problem with the quantum Cheshire cat paradox is that its original claim, that the particle and its property, such as spin or polarization, separate and travel along different paths, may be a misleading representation of the actual physics of the situation.
“We want to correct this by showing that different results are obtained if a quantum system is measured in different ways, and that the original interpretation of the quantum Cheshire cat only comes about if you combine the results of these different measurements in a very specific way, and ignore this measurement-related change,” said Holger Hofmann, a professor at Hiroshima University.
The team analyzed the Cheshire cat protocol by examining the relation between three different measurements regarding the path and polarization of a DOI: 10.1088/1367-2630/ad0bd4
The research team includes Jonte R. Hance, Ming Ji, and Holger F. Hofmann from the Graduate School of Advanced Science and Engineering, Hiroshima University. Hance is also a research associate in the Department of Electrical and Electronic Engineering at the University of Bristol.
The research was funded by Hiroshima University’s Phoenix Postdoctoral Fellowship for Research, the