I learned the principles of quantum physics and the basic mathematical techniques quite some time ago. The only discussion of quantum entanglement concerned the EPR paper. There have been many advances in the field since that time, including the somewhat mysterious phenomenon of quantum teleportation. My background is primarily optics, ultrafast laser applications, ultrahigh vacuum systems, photo-electron beams, electron microscopy, some materials science, grown carbon nanotubes ... designing and building systems, plus a lot of industrial applications. I understand the process for generating entangled photons by means of down conversion, though it is a very inefficient process. In this case the initial photon is replaced by a pair while conserving total energy and momentum. The entanglement process occurs when the two photons are "created". My current understanding of the physics of quantum entanglement is that the entangled quantum particles must share a superposition of states. Question #0: Is it true that every set of quantum entangled particles must be in a superposition of states? Question #1: is the act of particle creation the only way to create entangled pairs? Question #1.a: what other ways have been demonstrated? Question #1.b: what limits the efficiency of the entanglement "process"? Question #2: Is it possible to entangle dissimilar particles - e.g., a neutron and a photon? In the EPR paper only conserved properties were entangled. But there are many quantum observables; each observable corresponds to a definite quantum state - many are discrete, but others are continuous. Some represent conserved quantities, others may not. Question #3: Is every quantum property capable of being entangled? It may be convenient to lock this thread, and then I will ask the individual questions one at a time, referring back to this as a common starting point for my continuing education.