Here is "The PANDA"



Actually according to this he just made it possible to scale the data they need for Panda, hes not actually done the quality rating itself:

How Google's Panda Update Changed SEO Best Practices Forever - Whiteboard Friday | SEOmoz

If you look at this CV it confirms he worked on speeding up machine learning.

" But basically before Panda, machine learning scalability at Google was at level X, and after it was at the much higher level Y. So that was quite nice. Thanks to Navneet, right now they can scale up this machine learning."

• Using idealizing kernels to develop distance metrics incorporating user preferences
for high-dimensional data
• Design of a real time web page classifier for text and image data
 
"The sites that people like more, they put in one group. The sites that people like less, they put in another group. Then they look at tons of metrics....they use those in a machine learning process to essentially separate the wheat from the chaff."

This reminds me of the work done by the highest paid programmers in the world - financial algorithms. No surprise finance people tend to hire search people and digital signal processing experts since's they're essentially taking a massive amount of data (share prices, etc) and finding patterns in it.