Apple iPad 3 Retina display confirmed by iFixit18
is not compatible and thoughts of splicing wires to make the panel work were quickly quashed. But while iFixit could not get the screen powered up, it was able to look at the two panels under a microscope just like MacRumors did, and came to the exact same conclusion: the number of pixels on the Apple iPad 3 screen are four times the number on the Apple iPad 2. That means that the resolution on the new display is double that of the prior model at 2048×1536. In case you need the precise numbers, there are 786,432 pixels on the 9.7 inch iPad 2 display. The iPad 3 will have 3,145,728 pixels. Bottom line? The Apple iPad 3 has a Retina display.
Wait. Didn't none other than the late Steve Jobs say that a device had to have a pixel density of 300ppi or more to have a Retina display? Yes he did, but as iFixit explains in the video below, because a tablet is held further from the eyes than a phone, the Apple iPad-any tablet really-should be held to a pixel density of only 240 ppi or higher to be considered a Retina display. At 2048x1536, the iPad 3 has a 264ppi.
source: iFixit via Geek.com