  Combining high and low probability densities in intensity hybrids, we study
some of their properties in double-slit setups. In particular, we connect to
earlier results on beam attenuation techniques in neutron interferometry and
study the effects of very small transmission factors, or very low counting
rates, respectively, at one of the two slits. We use a "superclassical"
modeling procedure which we have previously shown to produce predictions
identical with those of standard quantum theory. Although in accordance with
the latter, we show that there are previously unexpected new effects in
intensity hybrids for transmission factors below $a\lesssim 10^{-4}$, which can
eventually be observed with the aid of weak measurement techniques. We denote
these as quantum sweeper effects, which are characterized by the bunching
together of low counting rate particles within very narrow spatial domains. We
give an explanation of this phenomenology by the circumstance that in reaching
down to ever weaker channel intensities, the nonlinear nature of the
probability density currents becomes ever more important, a fact which is
generally not considered - although implicitly present - in standard quantum
mechanics.
