Solution

ID: past-exam-of-the-computer-science-course-of-the-university-of-oxford/2020/quantum-information/2/b/iii/solution

The corresponding conditional vectors are and . The second has a nonzero component while the first does not, so they are linearly independent. Therefore the third state is also entangled. Orthogonality of these two conditional vectors is not required for this conclusion.
For an independent matrix check, expanding the second factor gives
The original expression is normalized because its two first-wire factors are orthogonal: its squared norm is , despite the overlap between and on the second wire.

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