Reliable information transmission through Gaussian loss channels using Gottesman-Kitaev-Preskill codes*

Generalizing the concept of (classical) channel capacity in Shannon information theory, quantum channel capacity quantifies the amount of quantum bits per channel use that can be transmitted reliably, upon optimal quantum error correction, with vanishing decoding error in the limit of infinitely many channel uses. Among various types of quantum channels, Gaussian thermal loss channels are of particular interest because they model realistic optical communication channels, and their quantum capacities are determined up to (at most) a constant gap between a lower and upper bound. Here, we consider an explicit quantum communication protocol using the Gottesman-Kitaev-Preskill (GKP) code, and report that the GKP code, although not designed to correct loss errors, nevertheless can achieve the quantum capacity of the Gaussian thermal loss channel up to a bounded constant offset.