Fig. 1: Superdense colour code.
From: Scaling and logic in the colour code on a superconducting quantum processor
a, Example tile in the bulk of a red, green and blue hexagonal lattice used for the superdense colour code. The lattice is embedded on a square grid of data qubits (golden circles labelled D1–D6) and X/Z auxiliary qubits (red, green and blue circles), with their connectivity indicated by solid grey lines. b, Superdense syndrome extraction circuit for the tile shown in a (see the main text). c, Distance-5 colour code qubit, with one of the distance-3 qubit subsets outlined in purple. Data qubits included in the logical operators XL and ZL are circled and connected by a solid black line. Red arrows indicate qubit pairs interchanged for the implementation of the colour code on our quantum device. d, Deformed code layout after interchanging the qubits to ensure that each readout line contains only data or auxiliary qubits. The readout lines are oriented diagonally from top left to bottom right (two dashed grey lines).
