ABSTRACT
This chapter presents an account of work carried out on metastable atomic hydrogen to measure the polarisation correlation of the two photons produced in the decay process and to test Bell’s inequality and ideas of enhancement. It describes the theory of the two-photon decay will be discussed and an appropriate form of Bell’s inequality. Experiments to test Bell’s inequality usually involve placing a linear polariser and detector diametrically on each side of a source. The measurements of the circular polarisation correlation were not in a form suitable to test Bell’s inequality directly and indicated that the imperfections of the nominally achromatic quarter-wave plates were such as to render unlikely a successful test along these lines. Measurements of the linear and circular polarisation have been carried out and Bell’s inequality put to the test.
