Approximating projections by quantum operations
arXiv:2203.02627 · doi:10.1016/j.laa.2023.01.008
Abstract
Using techniques from semidefinite programming, we study the problem of finding a closest quantum channel to the projection onto a matricial subsystem. We derive two invariants of matricial subsystems which are related to the quantum Lovász theta function of Duan, Severini, and Winter.
Final version; minor changes