The <trace distance> and <quantum fidelity>, in the unsquared convention, are
$$
\boxed{D(\rho,\sigma)=\frac12\|\rho-\sigma\|_1},
\qquad
\boxed{F(\rho,\sigma)
=\operatorname{Tr}\sqrt{\sqrt\rho\,\sigma\sqrt\rho}}.
$$

Solution

Past exam of the mathematics course of the University of Cambridge / 2021 / iii / Paper 323 / 4 / a / i / Solution

 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2021/iii/paper-323/4/a/i/solution