Entanglement and the Joining of History

In our story, just as we did not allow splitting to happen in a way that would allow communication faster than light, so we must insure the same for interference. When a wave of differentiation, set off by two different values, x and y of some variable has left an object, the object is entangled with all the differentially affected objects. And here we have a lovely little diagram explaining what not entangled is about. So our rule, in short, is that interference can happen only in objects that are unentangled with the rest of the world. We don't fully have it yet, this evidence, we will when quantum computers are built.