Quantum reference frame changes for general and imperfect frames
In plain words
Describing physics from the viewpoint of a quantum particle needs rules for switching viewpoints. Several frameworks give such rules for idealized frames; for realistic frames such as small quantum clocks they disagree or are undefined.
Precise statement
Construct transformations between quantum reference frames for arbitrary symmetry groups (including non-Abelian, e.g. SU(2) rotations) and non-ideal frames (finite-dimensional, with non-orthogonal orientation states), and prove equivalence or a precise relation between the perspective-neutral (constraint-based), operational and perspectival approaches. An answer is one framework with proofs that each existing one is a special case, or a stated inequivalence.
What would settle it
Published theorems relating the frameworks for general groups and non-ideal frames.
Status in the literature
Frameworks for general groups and some non-ideal frames exist; their full equivalence is proved only for restricted classes of frames.