  A moving dielectric medium can displace the optical path of light passing
through it, a phenomenon known as the Fresnel-Fizeau optical drag effect. The
resulting displacement is proportional to the medium's velocity. In this
article, we report on an anomalous optical drag effect, where the displacement
is still proportional to the medium's speed but along the direction opposite to
the medium's movement. We conduct an optical drag experiment under conditions
of electromagnetically-induced transparency and observe the transition from
normal, to null, to anomalous optical drag by modification of the two-photon
detuning.
