Completely positive projections and biproducts
arXiv:1308.4557 · doi:10.4204/EPTCS.171.7
Abstract
The recently introduced CP*-construction unites quantum channels and classical systems, subsuming the earlier CPM-construction in categorical quantum mechanics. We compare this construction to two earlier attempts at solving this problem: freely adding biproducts to CPM, and freely splitting idempotents in CPM. The CP*-construction embeds the former, and embeds into the latter, but neither embedding is an equivalence in general.
In Proceedings QPL 2013, arXiv:1412.7917