>>12437921yes but you are talking about something on the order of a quantum field at this point. You do understand that you are talking about two particles in a quantum field? We're not talking about occlusion and "illusory" objects such as shadows, we're talking about point particles and their wavefunctionality.
Just knowing the particle exists and is sustained in its location without becoming subject to decay, like for example, the center particle in a grid of diamonds, a very stable array, can allow us to achieve stability in FTL communication.
Your boundary constraint are the field constants, like vacuum energy. Which are extremely low in density and would not interfere with FTL propagation of causally inferred information via spin state determination.