PBS Space Time S2021 E18 How Quantum Entanglement Creates Entropy

Entropy is surely one of the most perplexing concepts in physics. It’s variously described as a measure of a system’s disorder - or as the amount of useful work that you can get from it - or as the information hidden by the system. Despite the seeming ambiguity in its definition, many physicists hold entropy to be behind one of the most fundamental laws of physics.