Fellow time-nuts, Over a year and a half or so, we have been starting to grasp the various aspects of the cross-correlation catastrophe. This consists of two properties, one is the insertion of anti-correlated noise into the two channels, and then when cross-correlated it produced a subtracting "energy" reducing the level and even inverting the sign. Thus, there is a bias in the estimation and overoptimistic or even seemingly physically impossible (until you understand the mechanics). This have been occupying the mind of some of the best folks we have in the field. Just interacting and discussing this with some of them have been a great learning experience. Anyway, here is a write-up that covers it sufficiently: http://arxiv.org/abs/1512.06160 So, now you know why I look suspiciously at too low noise-levels. Cheers, Magnus