This is not one of the standard jQuery effects when an AJAX call sets the opacity of the content to 50% (or something like that), and when the next page loads, it deletes the current content, removes the opacity, applies new data and the presentation port lights up at the top screen.
It should be very easy to replicate.
EDIT
Ok, so I hit something together in jsFiddle , this is a very quick and dirty attempt to replicate the transition to a Google page, remember that my jQuery code is for demo purposes, you want to use AJAX callbacks to change the state of the content.
http://jsfiddle.net/puKBQ/
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