What solutions are available for using iPad as an extended desktop?
You will need an app to get this working properly, the nice new features in Mavericks are still essentially limited to traditionally connected displays via cables (DisplayPort/HDMI/Thunderbolt), rather than wireless connections.  There are many you can try, but my (unaffiliated merely personal preference) recommendation is Air Display.

Note that because the 2nd screen will be transferred over Wifi, you need to ensure that the iPad has a solid connection to the same LAN as your main Mac - being close to your Mac might be no good if they are both a distance away from the router...  As such, any usage of the iPad 2nd screen that requires fast refresh of window contents might not perform in any way like a proper monitor would, but it should be great for normal non video/gaming OS X apps.