A quantum spin model is a quantum Hamiltonian model that describes a system which consists of spins either interacting or not and are an active area of research in the fields of strongly correlated electron systems, quantum information theory, and quantum computing. The physical observables in these quantum models are actually operators in a Hilbert space acting on state vectors as opposed to the physical observables in the corresponding classical spin models - like the Ising model - which are commutative variables.