Vacuum Lightcone Fluctuations in a Dielectric

TL;DR

This paper models how electromagnetic vacuum fluctuations can cause measurable variations in the flight time of a probe pulse passing through a nonlinear optical material, serving as an analog for quantum gravity effects.

Contribution

It introduces a novel model linking vacuum fluctuations to observable optical effects and provides numerical estimates for fractional flight time fluctuations.

Findings

Fractional fluctuations in flight time can reach about 10^{-9} in realistic setups.

Vacuum fluctuations predominantly involve modes with wavelengths comparable to the slab thickness.

The model serves as an analog for quantum gravity lightcone fluctuations.

Abstract

A model for observable effects of electromagnetic vacuum fluctuations is presented. The model involves a probe pulse which traverses a slab of nonlinear optical material with a nonzero second order polarizability. We argue that the pulse interacts with the ambient vacuum fluctuations of other modes of the quantized electric field, and these vacuum fluctuations cause variations in the flight time of the pulse through the material. The geometry of the slab of material defines a sampling function for the quantized electric field, which in turn determines that vacuum modes whose wavelengths are of the order of the thickness of the slab give the dominant contribution. Some numerical estimates are made, which indicate that fractional fluctuations in flight time of the order of $10^{-9}$ are possible in realistic situations. The model presented here is both an illustration of a physical effect of vacuum fluctuations, and an analog model for the lightcone fluctuations predicted by quantum gravity.