What size are iPad Retina display wallpapers?

The new iPad (third generation) has a screen that quadruples the resolution of the iPad 2 screen.

For the best looking home and lock screen, iPad wallpaper should be sized to 2048 x 2048 pixels. Since graphics on the iPad rotate to landscape and portrait orientations, the wallpaper must be 2048 x 2048 to provide full coverage of the screen in both directions.