One-Shot Marton Inner Bound for Classical-Quantum Broadcast Channel

We consider the problem of communication over a classical-quantum broadcast channel with one sender and two receivers. Generalizing the classical inner bounds shown by Marton and the recent quantum asymptotic version shown by Savov and Wilde, we obtain one-shot inner bounds in the quantum setting. Our bounds are stated in terms of hypothesis testing and one-shot max divergences. These results give a full justification of the claims of Savov and Wilde in the classical-quantum asymptotic iid setting; the techniques also yield similar bounds in the information spectrum setting. We obtain these results using a different analysis of the random codebook argument; our method yields a classical one-shot Marton bound with a common message and a classical one-shot mutual covering lemma based on rejection sampling.