Given a quantum channel — that is, a completely positive trace-preserving linear map — as the only communication resource available between two parties, we consider the problem of characterizing the set of classical noisy channels that can be obtained from it by means of suitable classical-quantum encodings and quantum-classical decodings, respectively, on the sender’s and the receiver’s side. We consider various classes of linear witnesses and compute their optimum values in closed form for several classes of quantum channels. The witnesses that we consider here are formulated as communication games, in which Alice’s aim is to exploit a single use of a given quantum channel to help Bob guess some information she has received from an external referee.

中文翻译：

---

量子通道可实现的输入输出相关的最佳见证的显式构建

给定一个量子信道——即一个完全正的保迹线性映射——作为两方之间唯一可用的通信资源，我们考虑通过合适的经典噪声信道来表征可以从中获得的经典噪声信道集的问题。 - 分别在发送方和接收方的量子编码和量子经典解码。我们考虑各种类别的线性见证，并以封闭形式为几类量子通道计算它们的最佳值。我们在这里考虑的证人被表述为交流游戏，其中 Alice 的目标是利用给定量子通道的单次使用来帮助 Bob 猜测她从外部裁判那里收到的一些信息。