= Holevo-Schumacher-Westmoreland theorem
{c}
For a finite-dimensional memoryless <quantum channel>,
$$
C(\Lambda)=\lim_{n\to\infty}\frac1n\chi^*(\Lambda^{\otimes n}).
$$
The <Holevo bound> controls information obtainable from an output ensemble, while collective decoding makes rates below the corresponding coding expression achievable. The <Holevo capacity> needs regularization because input states can be entangled across channel uses. https://cs.uwaterloo.ca/~watrous/TQI/TQI.8.pdf[Watrous's channel-coding chapter] states and develops the classical-capacity theorem.
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