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.
We experimentally studied the electromagnetically induced transparency (EIT) in cesium (Cs) vapors under a three-level V-configuration system. Two independent diode lasers were employed in locked and scanning mode, respectively, for pumping and probing the atomic media. A probe laser was scanned across 6S 1/2 (F = 4) to all subsutructures of 6P 3/2 (F ′ = 5, F ′ = 4 and F ′ = 3) and the pump was locked at F ′ = 5 or F ′ = 4 or F ′ = 3 of 6P 3/2 . A good agreement of the experimental results with theoretical simulations was observed. The intensity and magnetic field dependence of the EIT spectrum in a V-type system of Cs atoms was also studied.
We present an idea for the doubly tagged delayed-choice tunable quantum eraser in a cavity QED setup, based on fully controlled resonant as well as dispersive atom-field interactions. Two cavity fields, bound initially in the Bell state, are coupled to a three-level atom. Such an atom is initially prepared in the coherent superposition of the lower two levels and is quite capable of exhibiting Ramsey fringes if taken independently. It is shown that the coherence lost due to tagging can not only be retrieved but that the fringe visibility/ path distinguishability can also be conditionally tuned in a delayed manner through local manipulation of the entangled cavity fields. The stringent condition here is the retainment of the system's coherence during successive manipulations of the individual cavity fields. Such a quantum eraser, therefore, prominently highlights the links among all the counterintuitive features of quantum theory including the conception of time, measurement, state vector reduction, coherence and information in an unambiguous manner. The schematics can be straightforwardly extended to a multipartite scenario and employed to explore multi-player quantum games with the payoff being strangely decided through delayed choice setups.
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