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tags: mathematics obsolete
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Frederik vom Ende
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edited tags; edited title
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Adam Zalcman
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Partial trace Can we express $\mathrm{tr}_A((A\otimes B)\rho_{AB})$ in terms of $A$, $B$, $\rho_A$ and tensor product operations$\rho_B$?

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JRT
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Partial trace and tensor product operations

For a density matrix $\rho_{AB}$ and some operators $A, B$, is there a way to express

$$\text{Tr}_A((A\otimes B)\rho_{AB})$$

using the reduced states $\rho_A$ and $\rho_B$ and operators $A$ and $B$? Note that when $A$ is the identity operator, this is indeed possible and one has

$$\text{Tr}_A((I_A\otimes B)\rho_{AB})= B\rho_{B}$$

as shown here.