The entangled measurement state is not a paradoxical superposition of the detector

TL;DR

The paper clarifies that the entangled measurement state is a superposition of correlations, not a paradoxical superposition of macroscopic detector states, resolving longstanding concerns about the measurement problem.

Contribution

It demonstrates through nonlocality experiments that the measurement state involves superpositions of correlations, not macroscopic superpositions, offering a new perspective on quantum measurement.

Findings

Measurement state is a superposition of correlations, not macroscopic superpositions.

Nonlocality experiments reveal the true nature of entangled states.

The paradox of Schrödinger's cat is resolved by understanding the superposition as correlations.

Abstract

The entangled state that results when a detector measures a superposed quantum system has spawned decades of concern about the problem of definite outcomes or "Schrodinger's cat." This state seems to describe a detector in an indefinite or "smeared" situation of indicating two macroscopic configurations simultaneously. This would be paradoxical. Since all entangled states are known to have nonlocal properties, and since measurements have obvious nonlocal characteristics, it's natural to turn to nonlocality experiments for insight into this question. Unlike the measurement situation where the phase is fixed at zero for perfect correlations, nonlocality experiments cover the full range of superposition phases and can thus show precisely what entangled states superpose. For two-state systems, these experiments reveal that the measurement state is not a superposition of two macroscopically different detector states but instead a superposition of two coherent correlations between distinct detector states and corresponding system states. In the measurement situation (i.e. at zero phase), and assuming the Schrodinger's cat scenario, the entangled state can be read as follows: An undecayed nucleus is perfectly correlated with an alive cat, AND a decayed nucleus is perfectly correlated with a dead cat, where "AND" indicates the superposition. This is not paradoxical.