Discussion on the Implications of Single Photon in Double Slit Interference and Delay Selection Experiments

Dmitri L. Khokhlov

Huei Peng

We have performed cross-double-slit experiment and delayed-choice-cross-double-slit experiment, denoted as extended double-slit experiments. The cross-double-slit experiments show that the cross-double-slit apparatus creates not only two interference patterns, but also four cross-interference-patterns, which are created by two double-slit. The delayed-choice-cross-double-slit experiments disclose new phenomena: (1) photons behave as both wave and particle in the same experiment simultaneously, which violate Bohr’s complementarity; (2) the cross-interference-pattern is created by one double-slit and one single-slit; (3) photons passing through the same slit behave as both wave and particle, referred it as the Wave-Particle-Paradox, which demands extensive study. We suggest to re-study wave-particle duality.

Axel Heuer, Dirk Puhlmann, R. W. Menzel

Particle and wave like properties of photons can impressively be demonstrated in Young’s double slit experiment. Usually, measurements behind the slit provide information either about the path of the single photons or interference can be observed. Today the question of “which-slit” versus “interference” in the double-slit configuration is as relevant as it was in the early days of quantum mechanics. To gain deeper insight we set up an experiment using a pair of photons generated by SPDC pumped with a higher order mode (TEM 01 ). One of the SPDC photons, the signal photon, was used to illuminate the double slit and measure the single photon interference behind it. The other photon, the idler photon, was used in a reference measurement at the position of the slit using a polarizing beam splitter. First, the signal photons were obtained at the position of the slit as a function of the position of the entangled idler photons in a coincidence measurement. From this coincidence measurement the “which-slit” information is available. In a second coincidence measurement the far field interference fringes were obtained for signal photons passing through one of the slits, only, selected by the position of the reference detector measuring the entangled idler photons. The newest results will be presented and discussed. This may provide new insights in the wave-particle dualism and thus inspire the discussion about the nature of photons.

Trent English

Alain Aspect, Philippe Grangier

Wolfgang Rueckner, Joseph Peidle

An apparatus for a double-slit interference experiment in the single-photon regime is described. The apparatus includes a which-path marker that destroys the interference as well as a quantum eraser that restores it. We present data taken with several light sources, coherent and incoherent and discuss the efficacy of these as sources of single photons.