ELI5: Explain Like I'm 5

Bound entanglement

Okay kiddo, imagine two balls that are made up of a silly putty-like substance. When the two balls touch each other, they stick together so firmly that no amount of pulling or stretching can separate them, no matter how far apart they are.

Similar to the two balls, in the world of quantum mechanics, there are particles that can become "entangled." Entanglement means that the particles become connected in a way that the properties of one particle instantly affect the properties of the other particle. But, unlike the silly putty balls, sometimes it's possible for the two entangled particles to be so connected that they can't be used to send messages, no matter how much they are moved apart. That's what we call "bound entanglement."

Think of it like a pair of gloves that only fit together, but you can't put one of them on one hand, and the other on the other hand. It's hard to explain why this happens, but scientists have discovered that some entangled particles only work together in a certain way, so no information can be extracted from them, making them useless for teleportation or communication.

In summary, bound entanglement is a phenomenon in which entangled particles have such strong connections that they can't be used to send information or messages, even if they are separated by great distances.