New answers tagged partial-trace
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Statevector from Density matrix of non-pure state
If you diagonalize the density matrix, the resulting eigenvectors are pure states of your mixture which gives the density matrix
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How to compute the partial trace of the state $|\psi\rangle = \sum_{k}c_k |k\rangle\otimes|k\rangle\otimes |k\rangle$?
TLDR; No, your answer should be
$$
\rho_B=\sum_k|c_k|^2|k\rangle\langle k|.
$$
You seem to have arrived at equation (3) from equation 2 essentially just by throwing away all the terms on qubits A and ...
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