Can one thing be two different things at once?
I think you are referring to quantum entanglement. This is not a theory; it is an observed physics property. When two photons are simultaneously produced during calcium decay, the two quanta are entangled. This means that the two particles act as though they were one. For example, if you detect the spin of one photon that will also be the spin of the other one. That doesn’t sound like much, but consider this. Spins are probabilistic; that is, they are not determined until actually detected (measured). Up to detection, the spin of any given photon pair could be either up or down. The fact that the other photon always (100% of the time) assumes the spin detected in the first one means that cousin photon is entangled. Here are two more really weird things about entangled quanta. First, it makes no difference how far apart the two quanta are. If they are entangled the one will always act as though it were one with the other. In experiments, they have detected entanglement kilometers apart
