Why shot noise usually cannot detect pairing in mesoscopic superconducting tunneling devices

Shot noise is a powerful tool for determining the effective charge in mesoscopic systems. It can detect electron pairing in superconductors, where shot noise changes from q=1e noise to q=2e noise. Here, I will present our shot noise results in typical mesoscopic superconductor-insulator-superconductor junctions using our newly developed low temperature noise amplifier. Our results indicate that the shot noise does not reflect the q=2e superconducting state but instead stays at a level corresponding to single electron charges, q = 1e.  I will show that this is caused by the fact that the large number of low-transparency channels obscure the shot noise from q=2e process. Our results indicate that the typical transparencies in mesoscopic junctions will suppress the q=2e shot noise and that controlling the transparency is key for detecting pairing in mesoscopic superconducting junctions.