Caeleste announced it demonstrates 0.5e on noise in 4T pixel:
"This 4T pixel, in a 0.18µm CMOS technology, has high fill factor and is compatible with frontside and backside illumination. The pixel has a very high charge to voltage conversion. In the present configuration we now demonstrate less than 0.5 electronsRMS read noise in the dark.
We will disclose more details on this proprietary technology at upcoming scientific conferences. We invite interested groups willing to provide independent confirmation of our results to contact us. Applications are in low noise and/or low light imaging, i.e. in virtually all imaging domains."