I liked Ors answer, but it is built on the premise that it is a single operator. The laws of physics indicate this probably not the case, and instead direct us to it being a number of sleighs, with Santa just being the boss of the company.
I disagree with both Ors and Ironraven. Santa is obviously a singular being having the ability to go into a superpositioning state as described in the Copenhagen interpetation of quantum mechanics. His wave function would cover all the locations of children in the world. He doesn't have to worry about collapsing into a settled state because he can't be observed: children fall asleep before he arrives, adults don't believe he exsists and so are blind to him. The "Santa-blindness" of adults extends to the point that they believe THEY were the ones who bought/wrapped/placed the presents under the tree, not Santa.
The ability to go into quantum superpostion wave function removes all the difficulties of high-speed travel, too-small chimneys, a gift bag bigger on the inside than outside, raindeer poop, etc...
It makes absolutely perfect sense.
Especially if you're holding a grudge against a
cat.
-Blast