Signal velocity, causality, and quantum noise in superluminal light pulse propagation.
We consider pulse propagation in a linear anomalously dispersive medium where the group velocity exceeds the speed of light in vacuum ( c) or even becomes negative. A signal velocity is defined operationally based on the optical signal-to-noise ratio, and is computed for cases appropriate to the recent experiment where such a negative group velocity was observed. It is found that quantum fluctuations limit the signal velocity to values less than c.
Kuzmich
A
A
NEC Research Institute, 4 Independence Way, Princeton, New Jersey 08540, USA.
Dogariu
A
A
Wang
L J
LJ
Milonni
P W
PW
Chiao
R Y
RY