# Spin polarization-scaling quantum maps and channels

## TL;DR

This paper introduces a new class of quantum maps for spin-$j$ particles that model the decrease of spin polarization, analyzing their positivity, entanglement-breaking properties, and differences across spin values.

## Contribution

It defines spin polarization-scaling maps for arbitrary spin-$j$ particles and characterizes their positivity and entanglement properties, highlighting differences from spin-$rac{1}{2}$ cases.

## Key findings

- Conditions for positivity and complete positivity are derived.
- Maps can be entanglement breaking under certain parameters.
- Specific analysis for spin-1 particles is provided.

## Abstract

We introduce a spin polarization-scaling map for spin-$j$ particles, whose physical meaning is the decrease of spin polarization along three mutually orthogonal axes. We find conditions on three scaling parameters under which the map is positive, completely positive, entanglement breaking, 2-tensor-stable positive, and 2-locally entanglement annihilating. The results are specified for maps on spin-$1$ particles. The difference from the case of spin-$\frac{1}{2}$ particles is emphasized.