> which means that the choice of another waveform including, say, an additional particle off to the side, would imply that the entanglement -- which is supposed

> which means that the choice of another waveform including, say, an additional particle off to the side, would imply that the entanglement -- which is supposed to be the behaviour being described, not the theory used to describe it -- actually changes. But the entanglement between A and B _doesn't_ change by adding C. "Entangled" is the negation of "separable". If A and B can be described by a wavefunction that looks like (wavefunction A)x(wavefunction B), then we say the system AB is separable. This means, essentially, that A and B can be considered independent. If we can't write the wavefunction of AB as a product, then we say AB are entangled. Now, I hope that it is more clear that adding C to the side results in a wavefunction for ABC that is (wavefunction AB)x(wavefunction C). The entanglement of AB is unchanged, since the AB part of the ABC wavefunction is unchanged. All we have done is add a C part to the wavefunction, but this C part is not entanglement with AB.