Apparatus for intensity measurements of interference patterns

László Nádai, J. Bokor, A. Edelmayer

Sherwood I. Parker

Apparatus is described which produces an interference pattern using only one photon at a time. It can be used in a lighted room—no significant dark adaption is needed to see the pattern, even at the one-photon level. The number of photons per second producing the pattern is measured in the same apparatus with a photomultiplier.

William Yang

The goal of this project was to develop an apparatus to measure the coherence length of the light waves produced by different lasers.The coherence length is the distance over which two interacting waves maintain a constant relative phase.The method selected to achieve the goal of the project was to introduce the laser light into a modified Michelson interferometer arrangement while observing and measuring the resulting interference pattern. This pattern can be interpreted in terms of the properties of the laser light from which the pattern was produced, including, it was predicted, its coherence length. In order to characterize the apparatus and develop a means of interpreting the interference patterns, two different lasers were used: a red diode laser taken from an inexpensive laser pointer, and a red He-Ne laser. As part of this project the quantum eraser phenomenon and bandwidth of the diode and He-Ne lasers were also investigated. The project is continuing an investigation of the utility of the apparatus for coherence length measurements.

J.P. MATHIEU

L. Nidai, Péter Várlaki

Time-correlated single photon counting is a technique to record low level light signals with very high time resolution. We first describe the experimental apparatus and briefly outline the statistical interpretation of the measurement series. After, we propose a stochastic model for the formulation of interference patterns based on doubly stochastic autoregressive model class. We suggest the application of optimal filtering technique conceived in [R. J. Elliott et al., (1997)] in order to estimate the underlying intensity process of the Poisson type measurement series. Finally, we present some results of the identification of realistic data that is although in coincidence with the general view of interference experiments, goes beyond the physical interpretation and may deepen our understanding of the quantum world.