When a light pulse propagates through a transparent,
linear, and anomalously dispersive medium, its group velocity
can exceed c,
or even become negative. We review recent experiments on superluminal
and negative group velocity in various physical systems. We further
study the velocity of signal transmission in these situations
by closely analyze the optical signal-to-noise ratio. We show
that quantum fluctuations limit the signal velocity to values
less than c.
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©Copyright 1999 KSU Department of Physics |