how big is it, and how big is the pot? and where are you located? is the tree outside full time?
i've had a lot of successes with potted trees (even quite small ones), heeling them in to the ground (pot and all), down to where the soil line in the pot matches the soil outside it. a bit of mulch on top, and even young trees should be pretty safe (barring rodents, dogs, etc). you wouldn't need to do that until late fall, when the leaves have already fallen and the tree is dormant. then you can pull it back out in the spring when risk of freezing roots is gone again.
i've had many different trees do fine, just in a pot outside all winter, but if you want a little more protection, heeling the pot in helps. the tree will definitely need a real winter, though, and would do much worse if you tried to bring it inside.