👉 Entanglement Entropy (EE) is a fundamental concept in quantum information theory that quantifies the amount of quantum entanglement between two subsystems of a larger quantum system. It measures the degree of correlation between these subsystems by calculating the von Neumann entropy of the reduced density matrix of one subsystem. When two particles are entangled, their joint state cannot be described as a simple product of individual states; instead, it exhibits correlations that increase the EE between them. As the subsystems become more entangled, the EE grows, reflecting stronger quantum correlations. This measure is crucial in understanding quantum many-body systems, quantum computing, and quantum communication, as it provides insights into the entanglement structure and the complexity of quantum states.
