RT Journal Article
T1 Unbounded number of channel uses are required to see quantum capacity
A1 Cubitt, Toby S.
A1 Elkouss Coronas, David
A1 Matthews, William
A1 Ozols, M.
A1 Pérez García, David
A1 Strelchuk, S.
AB Transmitting data reliably over noisy communication channels is one of the most important applications of information theory, and is well understood for channels modelled by classical physics. However, when quantum effects are involved, we do not know how to compute channel capacities. This is because the formula for the quantum capacity involves maximizing the coherent information over an unbounded number of channel uses. In fact, entanglement across channel uses can even increase the coherent information from zero to non-zero. Here we study the number of channel uses necessary to detect positive coherent information. In all previous known examples, two channel uses already sufficed. It might be that only a finite number of channel uses is always sufficient. We show that this is not the case: for any number of uses, there are channels for which the coherent information is zero, but which nonetheless have capacity
PB Nature Publishers Group
SN 2041-1723
YR 2015
FD 2015-03
LK https://hdl.handle.net/20.500.14352/24015
UL https://hdl.handle.net/20.500.14352/24015
LA eng
DS Docta Complutense
RD 8 abr 2025