As the goal of this book, we will provide an overview of the principles of quantum annealing, building upon the concepts developed so far. We formulate combinatorial optimization problems as the search for the minimum of a potential landscape, and explain the idea of leveraging quantum tunneling to approach the solution (Sect. 8.1). This concept is concretely implemented in terms of finding the most stable configuration of a spin Hamiltonian (Sect. 8.2). To clarify the implementation, we present a detailed discussion of a specific example, formulating a path-finding problemPath-finding problem (Sect. 8.3). Finally, as a supplement, we briefly explain how entanglement states emerge within quantum computation (Sect. 8.4).