Discrete-Event Simulation Unmasks the Quantum Cheshire Cat

Abstract

It is shown that discrete-event simulation accurately reproduces the experimental data of a single-neutron interferometry experiment [T. Denkmayr et al., Nat. Commun. 5, 4492 (2014)] and provides a logically consistent, paradox-free, cause-and-effect explanation of the quantum Cheshire cat effect without invoking the notion that the neutron and its magnetic moment separate. Describing the experimental neutron data using weak-measurement theory is shown to be useless for unravelling the quantum Cheshire cat effect.Magic and mystery, in the broad sense, have always been embraced by lots of people, including scientists. This also holds for the so-called mysteries in quantum mechanics. The central mystery of quantum mechanics, wave-particle duality (interference), and other mysteries like the Schrödinger's cat paradox (superposition), the Einstein-Podolsky-Rosen paradox (entanglement), and various others, including their application in quantum teleportation, quantum cryptography and quantum computation, do not only fascinate many scientists but also seem to capture the public imagination, resulting in many popular books and publications. These mysteries are foreign to quantum theory itself as this theory describes features of a collective of outcomes only. They are a consequence from attempts to explain what happens to single objects in thought or laboratory experiments as they do not appear in statistical quantities. Unfortunately, resolving mysteries is not as popular as the mysteries themselves. One reason for this might be that we humans simply like mysteries. Another reason for mystery cultivation may be found in the quote by Einstein "We can't solve problems by using the same kind of thinking we used when we created them". In other words, demystifying these so-called quantum experiments requires some out of the box thinking, that is one might have to leave one's comfort zone.Recently, a new quantum mystery called quantum Cheshire Cat, has grabbed a lot of media attention. The quantum Cheshire Cat displays mysterious behavior similar to that of the grinning Cheshire Cat in the novel "Alice's Adventures in Wonderland" by Lewis Carroll [1]. In this children's story the Cheshire Cat is able to slowly vanish beginning with the end of its tail, and ending with its grin, which remains for some time after the rest of the cat has disappeared. The scientific community has embraced the Cheshire Cat as a metaphor to explain several scientific phenomena. The "classical" optical Cheshire Cat effect has been demonstrated in an experiment with a mirror stereoscope allowing one eye of the viewer to see a person's face in front of a white background and the other eye to see a solid white background [2]. If the viewer looks at the smile of the face while a hand makes a slow sweeping motion in the visual field of the other eye, the motion causes the face to completely disappear leaving only the smile. This "non-quantum" Cheshire Cat effect is an optical illusion caused by binocular rivalry [2], a visual phenomenon in which percept...