Quantum entanglement
Although you can do some things to one particle to try to cause a change in its partner particle, you can't use this (by itself) to send information from one particle to another because it is only possible to control how likely the change will happen. The outcome of whatever measurement you make on a single particle is completely random, and so is the change that results in the partner particle. In other words, changing one particle may change its partner particle, but you cannot guarantee exactly which way you will influence them. Because scientists cannot control exactly what changes between entangled particles occur, it is not possible to use quantum entanglement alone to send messages. If you also send information about the state of the single particle classically (by phone, radio, carrier pigeon, etc.), you can use the entanglement they share to teleport the quantum state of one particle to another particle.