Denser Planar Color Codes

Abstract

We consider the 4.8.8 color code in a brickwork layout on the square lattice with nearest-neighbor gates. We identify periodic superdense circuits with twelve CNOT layers that appear to preserve the full distance of these codes. Including ancillas, the family uses $q=(2d^2+5d-5)/2$ physical qubits for distance $d$: asymptotically $2/3$ as many as the triangular 6.6.6 color code and $1/2$ as many as the rotated surface code at the same code distance. Circuit-level simulations targeting superconducting architectures demonstrate favorable scaling of 4.8.8 color codes at plausible physical noise rates, including both for planar codes and their toroidal cousins under periodic boundary conditions.

arXiv comment18 pages, 6 figures