  The title of this article is misleading. The authors have investigated a
resonator but not a tunneling barrier see also Refs.\cite{Winful2} The measured
superluminal group velocity and discussed is that studied on a Lorentz-Lorenz
oscillator by Sommerfeld and Brillouin a hundred years ago \cite{Brillouin}. It
is similar to the faster than light experiment by Wang et al. based also on
anomalous dispersion with a complex refractive index of a resonator
  \cite{Wang}.
  Tunneling, however, is understood and performed by electromagnetic evanescent
modes or by tunneling solutions of the Schr\"odinger equation, which have
purely imaginary wave numbers. The latter includes a purely imaginary
refractive index. Signals with purely evanescent frequency components can
travel at a superluminal velocity \cite{NimtzH,Nimtz1}. Inside the barrier
tunneling proceeds even instantaneously, i.e.by a process described by virtual
photons \cite{Stahlhofen}.
