Analysis of the two-photon radiation of metastable atomic hydrogen

Abstract

The Stirling two-photon coincidence experiment based upon the decay radiation of metastable atomic hydrogen has been applied to the measurements of angular and polarization correlations, an experimental confirmation of the Breit-Teuer hypothesis, Einstein-Podolsky-Rosen (EPR) experiments, and measurements of the two-photon coherence length and time. Based upon angular conservation and parity arguments, a two-photon state vector can be defined and used for polarization correlations of the two-photon radiation. The results of the Einstein-Podolsky-Rosen experiments with two-photon radiation from metastable atomic hydrogen clearly favour quantum mechanics over local realistic theories in common with all other published studies. However, by inserting an additional linear polarizer in one of the two detection arms (a three-polarizer method) it was possible experimentally to confirm the difference of almost 40% between the quantum-mechanical prediction and Bell’s limit for local realistic theories, thereby demonstrating the largest such difference in EPR experiments so far. The coherence time and length of the two-photon emission of metastable atomic hydrogen was measured by inserting retardation (“multiwave”) quartz plates orientated with their fast axis at 45° with respect to the linear polarization, which in turn is determined by the polarization direction of the linear polarizer in the other detection arm. A Stokes parameter analysis of the coincident two photons proves the coherent nature of the two-photon radiation emitted from metastable atomic hydrogen. The coherence length (lcoh = 350 nm) found in this way is extremely short, only about 1.5 times the medium wavelength of 243 nm of the two-photon radiation. The corresponding coherence time (lcoh = lcoh/c) is approximately 10−15s, which confirms that it is not determined by the long lifetime of the metastable 2S-state (≅ 1/8s). Reference will be made to a new and recent theoretical prediction of the preceding coherence parameters.