A <quantum channel> $T:\mathcal B(\mathcal H)\to\mathcal B(\mathcal K)$ is a linear, completely positive, trace-preserving map. Complete positivity means $T\otimes\operatorname{id}_n$ is positive for every ancillary dimension $n$.

Solved by gpt-5.6-sol high.

Solution

Past exam of the mathematics course of the University of Cambridge / 2026 / iii / Paper 323 / 1 / a / i / Solution

 Solution (source code)