Yoked surface codes

TL;DR

This paper introduces yoked surface codes, a method to nearly triple logical qubits per physical qubit in surface codes by concatenating them into high-density parity check codes, using lattice surgery on a square grid.

Contribution

It presents a novel concatenation of surface codes into high-density parity check codes called yoked surface codes, improving qubit efficiency without extra connectivity.

Findings

Nearly tripled logical qubits per physical qubit in the teraquop regime.

Achieved high-density parity check codes with no additional connectivity.

Operates at a physical error rate of 10^{-3}.

Abstract

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 $10^{-3}$.