We consider the private classical capacity of a quantum wiretap channel, where the users (sender Alice, receiver Bob, and eavesdropper Eve) have access to the resource of a shared quantum state, additionally to their channel inputs and outputs. An extreme case is maximal entanglement or a secret key between Alice and Bob, both of which would allow for onetime padding the message. But here both the wiretap channel and the shared state are general. In the other extreme case that the state is trivial, we recover the wiretap channel and its private capacity [N. Cai, A. Winter and R. W. Yeung, Probl. Inform. Transm. 40(4):318-336, 2004]. We show how to use the given resource state to build a code for secret classical communication. Our main result is a lower bound on the assisted private capacity, which asymptotically meets the multi-letter converse and which encompasses all sorts of previous results as special cases.

翻译：本文研究了量子窃听信道的私有经典容量问题，其中用户（发送方Alice、接收方Bob和窃听方Eve）除了信道输入和输出外，还可利用共享量子态资源。极端情况是Alice与Bob之间拥有最大纠缠态或共享密钥，两者均能实现对消息的一次性加密。但本文中窃听信道与共享态均为一般情形。另一种极端情况是共享态为平凡态，此时我们回归到经典窃听信道及其私有容量的研究框架[N. Cai, A. Winter and R. W. Yeung, Probl. Inform. Transm. 40(4):318-336, 2004]。我们阐述了如何利用给定的资源态构建保密经典通信编码方案。主要研究成果是给出了辅助私有容量的下界，该下界渐近满足多字母逆定理，且能涵盖各类先前研究成果作为特例。