The difference between these states and classical states of matter is that classically, materials exhibit different phases which ultimately depends on the change in temperature and/or density or some other macroscopic property of the material whereas quantum phases can change in response to a change in a different type of order parameter (which is instead a parameter in the Hamiltonian of the system, unlike the classical case) of the system at zero temperature – temperature does not have to change. The order parameter plays a role in quantum phases analogous to its role in classical phases. Some quantum phases are the result of a superposition of many other quantum phases.