[quote="Spyder fan"]a few thoughts
is it a true vacuum in the reservoir or just a reduced pressure?
The volume in the crossmember/vacuum tank doesn't seem to be that big.
Firstly how to prepare this state in practice is another matter. There are both practical and theoretical difficulties. First the question of matter quantum fields. The key idea here is that regions of space only evacuate through diffusion: we don't have any magic means of calling up all the particles in a region and saying "hey guys, could you all please shift to one side of this chamber now?" You simply place the region of space you want to evacuate in contact with another region of space with a lower particle density and let particles freely diffuse back and forth between the two. We can prepare low particle densities through piston apparatus and the like, and one could imagine in theory using pistons with non return valves over many cycles to achieve a high probability of no matter particles in a region (somewhat like the old joke about homeopathic procedures diluting medicine to below single molecule in the bottle concentrations), but in practice this procedure is hard to make perfect. Some of the practical difficulties (outgassing and so forth) are talked about in the Wikipedia article "Ultra-high Vacuum". Moreover, even if you did get rid of all matter particles, then your chamber walls are at nonzero thermodynamic temperature, so now the inside of the chamber contains blackbody radiation. This you cannot get rid of unless the chamber walls are at truly absolute zero thermodynamic temperature.
John