  A recently proposed experimental protocol for Quantum Gravity induced
Entanglement of Masses (QGEM) requires in principle realizable, but still very
ambitious, set of parameters in matter-wave interferometry. Motivated by easing
the experimental realization, in this paper, we consider the parameter space
allowed by a slightly modified experimental design, which mitigates the Casimir
potential between two spherical neutral test-masses by separating the two
macroscopic interferometers by a thin conducting plate. Although this set-up
will reintroduce a Casimir potential between the conducting plate and the
masses, there are several advantages of this design. First, the quantum gravity
induced entanglement between the two superposed masses will have no Casimir
background. Secondly, the matter-wave interferometry itself will be greatly
facilitated by allowing both the mass $10^{-16}-10^{-15}$kg and the
superposition size $\Delta x \sim 20 \mu$m to be a one-two order of magnitude
smaller than those proposed earlier, and thereby also two orders of magnitude
smaller magnetic field gradient of $10^4$Tm$^{-1}$ to create that superposition
through the Stern-Gerlach effect. In this context, we will further investigate
the collisional decoherences and decoherence due to vibrational modes of the
conducting plate.
