  In 1957, Everett proposed a new no-collapse interpretation of orthodox quantum mechanics (see Everett 1957a,b, 1973, Barrett 1999, the entry on Everett's relative-state formulation of quantum mechanics, the entry on the many-worlds interpretation of quantum mechanics, and references therein). The Everett interpretation is a no-collapse interpretation of quantum mechanics, where the evolution of quantum states is always according to unitary and linear dynamical equations (the Schrödinger equation in the non-relativistic case). In this interpretation, quantum states are fundamentally relative. Systems have relative states, which are derivable from the various branches of the entangled states. For example, consider again |ψ11&gt;. 