Interference of Quantum Fields-Lessons and Uses
The interference of the beams of light led to the foundations of wave optics and this motivated founding fathers of quantum mechanics to arrive at the wave equation for quantum particles like electrons. With the advent of quantum theory of light by Planck, Dirac pondered over how the interference would arise with single photons as these fundamental entities could not be broken in two parts like light waves. He introduced the idea of the quantum amplitudes for the paths which needed to be summed up coherently before finding the intensity or the photon detection probability. I will present a very important application of the interference among several paths to understand in clear physical terms the phenomena of super radiance ie the emergence of enhanced radiation from a system initially prepared in a collective state. I will show how how a collective state leads to several paths along which photon can be emitted. A constructive interference of these paths leads to super radiance where as a destructive interference leads to sub radiance.