Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2016/iii/paper-323/4/ii/solution
Past exam of the mathematics course of the University of Cambridge 2016 iii Paper 323 4 ii Solution by
Codex 0 Created 2026-10-03 Updated 2026-10-06
The coefficient matrix in the computational basis isFor a bipartite pure state, the partial traces give and . Therefore the requested reduced density matrices areThe columns of are orthogonal. Their norms are and , so normalizing them gives the orthonormal setWith and , a Schmidt decomposition isExpanding this expression reproduces the minus sign in the coefficient. The two reduced density matrices both have eigenvalues and , consistent with these Schmidt coefficients.
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