The journey from ising model to quantum variational methods — In this article, we discuss about Ising Model, Quadratic Unconstrained Binary Optimization (QUBO) model, similarities between ising and QUBO model, Adiabatic theorem, QUBO model to Quantum Variational Methods. Ising Model: Ising Model is used to study phase transition in Magnetic systems. phase transition means interaction of near by spins.