Ontological status of the quantum state in non-relativistic quantum mechanics

Ascertain the ontological status of the quantum state in non-relativistic quantum mechanics, clarifying whether the quantum state should be regarded as a physically real entity or as a non-physical (e.g., epistemic or relational) construct, to ground reasoning about states and their role when comparing scales in quantum field theory.

Background

The discussion on states versus dynamics in QFT emphasizes that the small-distance state is a quantum state of a field, not a classical microstate. The interpretation of this quantum state bears directly on whether coarse-graining in QFT should be viewed as a literal many-to-one mapping on states.

Because the ontological status of the quantum state remains unresolved even in non-relativistic quantum mechanics, this uncertainty propagates into QFT interpretative issues, affecting how state transformations across scales are understood.