Mehmet Emre Taşgın
Institute of Nuclear Sciences, Hacettepe University
07 January 2016, Thursday, 14:40
Cavid Erginsoy Seminar Room, Physics Department, 3rd floor
In a previous publication  we have demonstrated the unreliability of superluminal pulse propagation velocities in dye experiments . In this presentation, we study an optomechanical cavity both in the second-quantized and classical (electromagnetics) pictures. We face with an intriguing coincidence. (i) Cavity and output fields become single-mode nonclassical above a critical cavity-mirror coupling strength g>gcrt . Considering only the amplitudes of the reflected/transmitted fields, classically, we obtain an effective refractive index for the cavity. (ii) Interestingly, cavity index (Greens function) permits superluminal source-potential communication above the same critical coupling g=gcrt. Moreover, emergence of this coincidence is independent of the length and type of the cavity, as well as the actual values of the cavity and mirror damping.
We carry this incidence to a next step. We show that a single-mode quasi-particle excitation (e.g. photons) becomes nonclassical, when the identical particles —generating this excitation— get entangled. Hence, one may speculate on the following question. Can the quantum entanglement of such background particles correspond to the superluminal source-potential (unobserved) communication?
 M. E. Taşgın, Testing the reliability of a velocity definition in dispersive medium, Phys. Rev. A 86, 033833 (2012).
 L. J.Wang, A. Kuzmich, and A. Dogariu, Gain-assisted superluminal light propagation, Nature (London) 406, 277 (2000).
 D. Tarhan and M. E. Tasgin, Mutual emergence of noncausal optical response and nonclassicality in an optomechanical system, arXiv:1502.01294
 M. E. Tasgin, Single-mode nonclassicality criteria via Holstein-Primakoff transformation, arXiv:1502.00988
 M. E. Tasgin, Single-mode nonclassicality measure from Simon-Peres-Horodecki criterion, arXiv:1502.00992