Abstract
Unstable systems such as media with inverted atomic population have been shown to allow the propagation of analytic wave packets with group velocity faster than that of light, without violating causality. We illuminate the important role played by unstable modes in this propagation and show that the quantum fluctuations of these modes and their unitary time evolution impose severe restrictions on the observation of superluminal phenomena.
- Received 7 April 1998
DOI:https://doi.org/10.1103/PhysRevLett.81.2190
©1998 American Physical Society
