We nearly triple the number of logical qubits per physical qubit of surface codes in the teraquop regime by concatenating them into high-density parity check codes. These "yoked surface codes" are arrayed in a rectangular grid, with parity checks (yokes) measured along each row, and optionally along each column, using lattice surgery. Our construction assumes no additional connectivity beyond a nearest neighbor square qubit grid operating at a physical error rate of 10−3.
@article{arxiv.2312.04522,
title = {Yoked surface codes},
author = {Craig Gidney and Michael Newman and Peter Brooks and Cody Jones},
journal= {arXiv preprint arXiv:2312.04522},
year = {2023}
}