Approach to accurately measuring the speed of optical precursors
  Precursors can serve as a bound on the speed of information with dispersive medium. We propose a method to identify the speed of optical precursors using polarization-based interference in a solid-state device, which can bound the accuracy of the precursors' speed to less than $10^{-4}$ with conventional experimental conditions. Our proposal may have important implications for optical communications and fast information processing. 
Chuan-Feng Li, Zong-Quan Zhou, Heejeong Jeong, and Guang-Can Guo
quant-ph physics.atom-ph