An Analog Model for Quantum Lightcone Fluctuations in Nonlinear Optics
  We propose an analog model for quantum gravity effects using nonlinear dielectrics. Fluctuations of the spacetime lightcone are expected in quantum gravity, leading to variations in the flight times of pulses. This effect can also arise in a nonlinear material. We propose a model in which fluctuations of a background electric field, such as that produced by a squeezed photon state, can cause fluctuations in the effective lightcone for probe pulses. This leads to a variation in flight times analogous to that in quantum gravity. We make some numerical estimates which suggest that the effect might be large enough to be observable. 
L. H. Ford, V. A. De Lorenci, G. Menezes and N. F. Svaiter
gr-qc hep-th quant-ph