Even quantum sensors will need something (i.e., another sensor) to stabilize the vertical channel. The effect of imperfectly compensating the gravity component

Even quantum sensors will need something (i.e., another sensor) to stabilize the vertical channel. The effect of imperfectly compensating the gravity component out of the specific force measurements from the accelerometers leads to a positive feedback loop. Finite precision arithmetic and fundamental algorithm error (solving the Bortz equation) leads to errors that will grow in the horizontal direction as well.