  Decoherence may not solve all of the measurement problems of quantum
mechanics. It is proposed that a solution to these problems may be to allow
that superpositions describe physically real systems in the following sense.
Each quantum system "carries" around a local spacetime in whose terms other
quantum systems may take on nonlocal states. Each quantum system forms a
physically valid coordinate frame. The laws of physics should be formulated to
be invariant under the group of allowed transformations among such frames. A
transformation of relatively superposed spatial coordinates that allows an
electron system to preserve the de Broglie Relation in describing a double-slit
laboratory system-in analogy to a Minkowskian Transformation-is proposed. In
general, "quantum relativity" says is invariant under transformations among
quantum reference frames. Some conjectures on how this impacts gravity and
gauge invariance are made.
