4D and 5D Layer Codes through Color Routing

TL;DR

This paper generalizes Layer codes to 4D and 5D using color routing, achieving optimal parameters and modularity suitable for architecture constraints.

Contribution

It introduces a CSS code construction for 4D and 5D Layer codes that saturates theoretical bounds using color routing techniques.

Findings

Constructed 4D and 5D Layer codes with optimal parameters.

Achieved saturation of D=4,5 dimensional BPT bounds.

Codes are modular and suitable for architectures with limited physical dimensions.

Abstract

We introduce and explicit Calderbank-Shor-Steane (CSS) code construction that generalizes the Layer codes to $D=4,5$ dimensions. Much like its predecessor, the present construction is based on embedding quantum low-density parity check (qLDPC) codes; from an $[[n,k,d]]$ code with energy barrier $\Delta$, we obtain a $D=4,5$ dimensional Layer code with parameters $[[\Theta(n^{D/(D-2)}), k, \Theta(dn^{1/(D-2)})]]$ and energy barrier $\Omega(\Delta)$. Using good qLDPC codes as input, our construction saturates the $D=4,5$ dimensional BPT bounds exactly. The higher dimensional Layer Codes are modular, and thus well suited to architectures composed of modular network patches, despite our physical limitation to three dimensions. We overcome the hurdles encountered by previous generalization attempts through the use of \textit{color routing}, allowing us to resolve the structure of the check layers and line defects.