  The electromagnetic vacuum is known to have energy. It has been recently
argued that the quantum vacuum can possess momentum, that adds up to the
momentum of matter. This ``Casimir momentum'' is closely related to the Casimir
effect, in which case energy is exchanged. In previous theory it was treated
semi-classically. We present a non-relativistic quantum theory for the linear
momentum of electromagnetic zero-point fluctuations, considering an harmonic
oscillator subject to crossed, quasi-static magnetic and electric and coupled
to the quantum vacuum. We derive a contribution of the quantum vacuum to the
linear pseudo-momentum and give a new estimate for the achievable speed. Our
analysis show that the effect exists and that it is finite.
