Nonclassical Nature of Dispersion Cancellation and Nonlocal Interferometry

TL;DR

This paper clarifies that nonlocal dispersion cancellation is inherently quantum and cannot be explained by classical physics, highlighting fundamental differences between quantum and classical models in two-photon interferometry.

Contribution

It demonstrates that nonlocal dispersion cancellation has no classical analog and discusses limitations of local realistic models in explaining two-photon interferometry.

Findings

Nonlocal dispersion cancellation is incompatible with classical field theory.

Classical models can only explain local dispersion cancellation.

Local models for two-photon interferometry are not realistic when considering spatial extent.

Abstract

Several recent papers have shown that some forms of dispersion cancellation have classical analogs and that some aspects of nonlocal two-photon interferometry are consistent with local realistic models. It is noted here that the classical analogs only apply to local dispersion cancellation experiments [A.M. Steinberg et al., Phys. Rev. Lett. 68, 2421 (1992)] and that nonlocal dispersion cancellation [J.D. Franson, Phys. Rev. A 45, 3126 (1992)] is inconsistent with any classical field theory and has no classical analog. The local models that have been suggested for two-photon interferometry are shown to be local but not realistic if the spatial extent of the interferometers is taken into account. It is the inability of classical models to describe all of the relevant aspects of these experiments that distinguishes between quantum and classical physics, which is also the case in Bell's inequality.