Communication over a noisy quantum channel introduces errors in the transmission that must be corrected. A fundamental bound on quantum error correction is the quantum capacity, which quantifies the amount of quantum data that can be protected. We show theoretically that two quantum channels, each with a transmission capacity of zero, can have a nonzero capacity when used together. This unveils a rich structure in the theory of quantum communications, implying that the quantum capacity does not uniquely specify a channel's ability for transmitting quantum information. 1 arXiv:0807.4935v2 [quant-ph]
The superactivation of the quantum capacity of zero-capacity quantum channels was introduced by Smith and Yard REF .
Quantum Communication With Zero-Capacity Channels
Science 321, 1812 - 1815 (2008)
Physics Medicine