Quantum Communication With Zero-Capacity Channels

TL;DR

This paper demonstrates that two quantum channels with zero capacity can be combined to achieve nonzero quantum communication capacity, revealing new insights into quantum channel capacities.

Contribution

It introduces the concept that zero-capacity channels can be used together to enable quantum communication, challenging previous assumptions about channel capacities.

Findings

Two zero-capacity channels can have a nonzero combined capacity

Quantum capacity is not a complete measure of a channel's communication ability

Reveals complex structure in quantum communication theory

Abstract

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.