Experimental observation of the Leggett-Garg inequality violation in classical light

Abstract

We present an experimental violation of the Leggett-Garg inequality in classical optics using only the polarization degree-of-freedom of a laser beam. Our results show maximum violations of the Leggett-Garg inequality.

Theory of Quantum Path Entanglement and Interference with Multiplane Diffraction of Classical Light Sources

“…The optimization study to maximize it to the calculated bounds [16] is left as an open issue. Besides that, a novel system design, i.e., MPD, violating LGIs with classical light sources is proposed in this article, complementing the recent experimental result in Reference [19] utilizing linear polarization degree of freedom of the classical light to violate LGIs. However, MPD utilizes photon-counting intensity detection with a significantly low experimental complexity.…”

“…• introduction and operator theory modeling of two novel quantum resources, i.e., QPE and QPI, denoting temporal correlations and the interference among quantum trajectories, respectively, in MPD while utilizing the tensor product structure for future quantum computing and communication architectures and foundational QM studies; • operator theory modeling of MPD-based resources QPE and QPI by combining history-based previous formulations of quantum histories [1,[3][4][5] with FPI formalism; • theoretical modeling and numerical analysis of MPD setup for the violation of LGI, with the ambiguous and no-signaling forms recently proposed by Emary in Reference [16], reaching > 1.2 of correlation amplitude numerically obtained for three-time formulation while leaving the maximization of the violation to the boundary levels as an open issue; • a novel setup, i.e., MPD, violating the ambiguous form of LGI with classical light sources complementing the recent experiment utilizing linear polarization degree of freedom of the classical light [19] while MPD setup with remarkably low complexity design utilizing classical light sources and photon-counting intensity detection; • theoretical modeling and numerical analysis of counterintuitive properties and examples of the interference among MPD-based Feynman paths denoted as QPI promising to be easily verified experimentally in future studies; • the modeling and numerical analysis of the coherence properties of the light sources in terms of spatial and temporal dimensions while discussing design issues for MPD setup with coherent light sources; and • discussion for future applications of QPE and QPI as quantum resources and experimental mplementations.…”

“…LGIs are violated reaching > 0.2 with a NIM-free formulation complementing the recent experimental implementation of the violation of LGI in Reference [19] utilizing linear polarization degree of freedom of the classical light with a photon-counting simple MPD setup of classical light. Besides that, it is an open issue to further design novel structures allowing the implementation of specific QPE states in analogy with GHZ states experimentally implemented for entangled trajectories [11].…”

Violating the Leggett-Garg inequalities with classical light

“…Violations with light have already been established [37][38][39][40], although with manifestly nonclassical states such as single photons. Violations using the polarization degree of freedom of a laser field were more recently shown to be possible [41]. However this violation is a particular implementation of a qubit to violate the LGI, whereas our proposal uses measurements on the coherent state itself to achieve the violation.…”

State-independent contextuality in classical light

“…On the other hand, recent investigations have also shown that many quantum phenomena, which are considered as the unique properties of quantum system, can also be simulated in classical systems, such as the violations of Clauser-Horne-Shimony-Holt (CHSH) Bell inequality in classical wave systems 33–43 , the Hardy’s thought experiment in classical light 44 , violating the Leggett-Garg inequality in classical optical systems 45 , the violation of Mermin’s inequality in classical nonseparability systems 46 , and so on. Recently, the state-dependent contextuality involving 5 variables has been studied in classical optical systems, and violations of the Klyachko-Can-Binicioglu-Shumovski (KCBS) inequality and its geometrical form (Wright’s inequality) have been demonstrated experimentally 47 .…”