Photon Statistics, Non-Classical Light and Quantum Interference

Abstract

In this chapter we hope to give an overview of studies in non-classical photon statistics and interference phenomena. We start by studying the generic optical measurement as illustrated in figure 1. The light is created in an emission process typically involving the transition of an atom from the excited state to the ground state with consequent emission of a ‘photon’ which is a manifestly quantum event. Photo-detection is also manifestly quantum in that a single electron is excited into the conduction band by the absorbtion of a ‘photon’ from the electro-magnetic field. The photo-electron can subsequently be amplified and detected in a pulse discriminator as a single ‘photon’ detection. With such a description the reader could be led to believe that the light propagating between the source and detector can be described simply as a stream of these particle like photons. In the first part of this article (section 2) I will describe measurements where interference effects can be largely ignored. The photodetection statistics are essentially those of a Poisson point process arising from the lack of correlation between individual emission events (section 2.1). When the source shows classical fluctuations these statistics are broadened. However our experimental goal in recent years has been to reduce the random fluctuations to below the Poisson value thus producing non-classical light with applications in low noise measurement.