ABSTRACT
Using correlated photons from spontaneous parametric downconversion, we have measured both the absolute quantum efficiencies and the time responses of four single-photon detectors. Efficiencies as high as (76.4 ± 2.3)% (at 702 nm) were seen, which to our knowledge are the highest reported single-photon detection efficiencies. An auxiliary retroreflection mirror was found to increase the net detection efficiency by as much as a factor of 1.19. The narrowest time profile for coincidences between two detectors displays a peak with 300 ps FWHM. We also investigated the presence of afterpulses and the effects of saturation and varying device parameters.
ABSTRACT
An electromagnetic search for magnetic monopoles of the minimum size predicted by Dirac, or of any larger magnitude, has been performed on 8.37 kilograms of lunar surface material. No monopole was found. This experimnent sets new limists on the production cross section for monopoles and on their occurrence in cosmic radiation.