Quantum entanglement, also called the quantum non-local connection, is a property of the quantum mechanical state of a system containing two or more objects, where the objects that make up the system are linked in a way that one cannot adequately describe the quantum state of a constituent of the system without full mention of its counterparts, even if the individual objects are spatially separated. Entanglement is one of the properties of quantum mechanics that caused many physicists, including Albert Einstein, to dislike this formulation of quantum mechanical theory. This book presents current research in the study of quantum entanglement, including entanglement in quantum-classical hybrids and quantum entanglement using multi dark soliton correlation for multivariable quantum routers.