Nonclassical nature of dispersion cancellation and nonlocal interferometry

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.

Time-resolved scattering of a single photon by a single atom

“…Our experimental results also contribute to a longstanding discussion about differences between heralded and ‘true' single photons32333435. The atomic excitation dynamics caused by heralded single photons matches well the one expected from ‘true' single photon states in our theoretical model, and therefore support a realistic interpretation of photons prepared in a heralding process.…”

Experimental Bell-inequality violation without the postselection loophole

“…One way to deal with this "postselection loophole" that affects all performed Bell tests using energy-time-or time-binentangled photons [14][15][16][17][18][19][20][21][22][23][24][25][26] is to add an extra assumption: the fact that a photon is detected at a specific time is independent * paolo.mataloni@uniroma1.it of the local experiment performed on that photon [27,29]. Therefore, even assuming ideal devices, Franson's setup can only rule out local LHV theories when this extra property is assumed.…”

Dispersion cancellation with phase-sensitive Gaussian-state light

“…[4][5][6], there is a unified Gaussian-state analysis capable of treating all of these nonclassical phenomena and more, e.g., the dispersion cancellation experiment of Steinberg et al [7] and the ghost imaging experiment of Pittman et al [8], both of which relied on biphoton explanations. Recently, Franson [9] has argued that his dispersion cancellation paradigm [10] differs from that of Steinberg et al in that the former is nonlocal, whereas the latter is not. More importantly, in Ref.…”

“…More importantly, in Ref. [9] Franson reviews various classical strawmen that have been suggested as providing explanations for his nonlocal dispersion cancellation and shows that each of them fails to reproduce one or more of the major features of quantum nonlocal dispersion cancellation. Hence, he concludes that nonlocal dispersion cancellation is a fundamentally quantum effect akin to violation of Bell's inequality.…”