Decay of quantumness in a measurement process: Action of a coarse-graining channel

TL;DR

This paper models a quantum measurement process involving a qubit system and an N-qubit apparatus, demonstrating how coarse-graining leads to the decay of quantum correlations and coherences without environmental interaction.

Contribution

It introduces a model showing how coarse-graining channels cause the decay of quantumness in measurement, providing insights into decoherence-like phenomena without environment coupling.

Findings

Coarse-graining reveals information about superposition coefficients.

Quantum correlations between system and apparatus diminish with strong coarse-graining.

Quantum coherences in the apparatus decay as coarse-graining increases.

Abstract

A model of a quantum measurement process is presented: a system consisting of a qubit in a superposition interacts with a measuring apparatus consisting of a N qubit state. Looking at the emerging, effective description of the apparatus given by the action of a coarse-graining channel, we have been able to recover information about the superposition coefficients of the system.We have also been able to visualize the death of quantum correlations between system and apparatus and the death of quantum coherences in the apparatus' effective state, in the limit of a strong coarse-graining action - a situation akin to decoherence, although it is not necessary to evoke any interaction with the surrounding environment.