Coding theorem and strong converse for quantum channels

We exhibit a possible road toward a strong converse for the quantum capacity of degradable channels. In particular, we show that all degradable channels obey what we call a “pretty strong” converse: when the code rate increases above the quantum ...

We revisit a fundamental open problem in quantum information theory, namely, whether it is possible to transmit quantum information at a rate exceeding the channel capacity if we allow for a non-vanishing probability of decoding error. Here, we ...

With the wringing technique developed by the first author for classical multiple access channels we show that the strong converse theorem holds also for quantum multiple access channels, if classical messages are transmitted.