Quantum Cheshire cat: a physically realistic interpretation by invoking entangled correlations

Abstract

The phenomenon of the quantum Cheshire cat (QCC) and its interpretation by Aharanov et al. [New J. Phys. 15, 113015 (2013)NJOPFM1367-263010.1088/1367-2630/15/11/113015], with the conjecture that any quantum entity can be disembodied from its physical attributes, has resulted in a heated debate leading to interpretational controversy as well as practical consequences. Here, we propose an experimentally testable and physically more realistic and logically plausible interpretation. We utilize a specifically engineered Mach–Zehnder-type interferometeric setup that is quite similar to the original QCC setup but with the slight difference that now a single-photon, bipartite entangled state traverses the interferometer such that each path is designated to a photon with different tags. With this specific setup, we demonstrate that the photon’s polarization is never physically separated from the photon itself. Rather, it becomes dormant and hence inaccessible along the designated interferometric path. We also generalize the schematics and show that any precisely oriented photon’s polarization that stands inaccessible or dormant re-emerges along the same spatially separated and isolated arm as we tune the polarization vector away from the selected angle. Thus our proposal persuasively proves that polarization is never stripped off the photon itself and instead becomes inaccessible along the interferometeric arm for a certain particularly selected orientation. The schematics further reveal that this inaccessibility of the photon’s polarization is not permanent, fixed, and universal, but rather it is entirely constrained to a specific orientation in the Hilbert space, governed by the particular pre- and post-selected state under two-state vector formalism.

Contextuality, coherences, and quantum Cheshire cats

“…We denote the property of the pre-and postselected particle having been on path 2 as {2}, and so call this claim NOT-{2}. (This was previously demonstrated by Saeed et al [20]. )…”

“…However, this interpretation of the protocol is controversial. Many have questioned how paradoxical the protocol actually is [18], with some saying the effect simply constitutes standard quantum interference [19] or entanglement [20,21], and others claiming the same result can be obtained using classical physics [22].…”