For the pure state $\sigma_{RQE}$ induced by a purification and <Stinespring dilation>, the <coherent information> is
$$
\boxed{I_c(\Lambda,\rho)=S(\sigma_Q)-S(\sigma_E)
=-H(R|Q)_\sigma}.
$$

Solution

Past exam of the mathematics course of the University of Cambridge / 2022 / iii / Paper 323 / 5 / b / Solution

{title2=$I_c(\Lambda,\rho)$}
{wiki}

For a channel output $Q$ and complementary environment output $E$, coherent information is $I_c(\Lambda,\rho)=S(Q)-S(E)=-H(R|Q)$ for a purification reference $R$.


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 Incoming links: Coherent information