Quantum Flags and New Bounds on the Quantum Capacity of the Depolarizing Channel
Quantum Flags and New Bounds on the Quantum Capacity of the Depolarizing Channel
A new upper bound for the quantum capacity of the $d$-dimensional depolarizing channels is presented. Our derivation makes use of a flagged extension of the map where the receiver obtains a copy of a state ${\ensuremath{\sigma}}_{0}$ whenever the messages are transmitted without errors, and a copy of a state ${\ensuremath{\sigma}}_{1}$, …