In a blink of an eye!
It seems that the booting up and log into dashboard processes of the Xbox One are pretty fast
Just take a look at this video below. It shows the Xbox One process of booting up and log into the dashboard in a matter of seconds.
If this is not a trick, it is impressive!
Official Source: http://www.youtube.com/watch?feature=player_embedded&v=EgHpGTHjwjk