Eric Fossum kindly allowed me to post a histogram of his and Jiaju Ma's image sensor that apparently achieves 0.32 e- rms noise on a single CDS read. It was achieved by minimizing the FD node capacitance as discussed in the March 2015 JEDS article:
"A Pump-Gate Jot Device With High Conversion Gain for a Quanta Image Sensor" by Jiaju Ma; Fossum, E.R.
The low readout noise manifests itself in a comb-like structure on the histogram, where the distance between the peaks is equivalent to 1e-. This preliminary result was first presented at IISW 2015 last week: