ever since the 'big bang', the universe haas been expanding. That means every thing is moving away from everywhere. The computations are not the same each time you start them up.
(unless you don't mind ending up in the belly of the star...)
It's true it is expanding. But we don't know the rate star systems might be pulled out with it. The calculations for the most part would be the same in the short period of time things are going on in the game. It is like in the show stargate sg1. After all them centuries the planets shifted and using the Earth based systems for the calculations, calculations had to be altered a little bit. So the quantum computers would only need some minor calculation alteration to account for spacial drift. These computers should at least be able to handle it. Especially for shorter jumps. I know these computers might not be as elaborate as those found in Star Wars. But even the Falcon only needed a few minutes for the calculations to be made for a jump into hyperspace. This is course assuming they had all galactic map info already programmed into their computers.