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Open Quantum Systems Decoherence Entanglement Theory Quantum Correlations

CPDNN quantum channels with qubit output are CPCP

arXiv
Authors: Hyunho Cha

Year

2026

Paper ID

30714

Status

Preprint

Abstract Read

~2 min

Abstract Words

91

Citations

N/A

Abstract

The resource theory for nonnegativity of quantum amplitudes distinguishes completely positive completely positive (CPCP) quantum channels from the larger and more tractable class of completely positive doubly nonnegative (CPDNN) quantum channels. It was left open whether there exists a qutrit-to-qubit quantum channel Φ:M3→ M2 that is CPDNN but not CPCP. We answer this question in the negative and prove the stronger statement that every CPDNN quantum channel Φ:Mn→ M2 is CPCP for every ninmathbb N. Equivalently, for qubit-output quantum channels the doubly nonnegative relaxation is exact.

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  • The resource theory for nonnegativity of quantum amplitudes distinguishes completely positive completely positive (CPCP) quantum channels from the larger and more tractable...

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References & Citation Signals

[1] DOI https://doi.org/arXiv:2603.16962 [2] arXiv https://arxiv.org/abs/2603.16962 [3] Publisher https://arxiv.org/abs/2603.16962

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