Quantum limitations on superluminal propagation

Unstable systems such as media with inverted atomic population have been shown to allow the propagation of analytic wavepackets 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.Comment: RevTeX 4 page

Using time reversal symmetry for sensitive incoherent matter-wave Sagnac interferometry

We present a theory of the transmission of incoherent guided matter-waves through Sagnac interferometers. Interferometer configurations with only one input and one output port have a property similar to the phase rigidity observed in the transmission through Aharonov-Bohm interferometers in coherent mesoscopic electronics. This property is connected to the existence of counterpropagating paths of equal length and enables the operation of such matter-wave interferometers with incoherent sources. High finesse interferometers of this kind have a rotation sensitivity inversely proportional to the square root of the finesse

Video signal enhancement system with dynamic range compression and modulation index expansion Patent

Video signal enhancement of signal component representing brightness of scene element in low contras

Television signal processing system Patent

Video signal processing system for sampling video brightness level