 Solution

ID: past-exam-of-the-computer-science-course-of-the-university-of-oxford/2023/quantum-information/1/a/i/solution

d \times d

ρ = ρ^{†}, v^{†} ρ v \geq 0 for every v \in C^{d}, Tr ρ = 1.

Equivalently, its eigenvalues are nonnegative and sum to one, with an orthonormal basis of eigenvectors.^[ref]

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