As others have mentioned, the double-split experiment is interesting in that when you leave a quantum system alone and let it travel through the double slit exp

As others have mentioned, the double-split experiment is interesting in that when you leave a quantum system alone and let it travel through the double slit experiment, the interference pattern occurs. If you "force" an entangled system into a particular slit, then you don't have a quantum entangled system by definition; the entanglement comes from the quantum interaction of the system and how we can only describe it via an entangled wave function. I think in terms of practical use cases, generally for entanglement, it allows for high amounts of encoding since the particular basis used to describe each individual constituent becomes coupled with one another e.g. (|PsiA, PsiB> = (|A1> + |A2> + ... + |An>) * (|B1> + B2> + ... + |Bn>)) allow for a high number of configurations of a problem space to be encoded. I suppose there could be some interesting optical phenomena used for optical experiments/pulsed lasers but you'd probably need to discuss this with an optics expert :-)