Diamond Circuits for Surface Codes

TL;DR

This paper introduces diamond circuits, a new construction for surface codes that improves qubit and measurement efficiency by using a mid-cycle, subsystem-based approach on Lieb lattices, with potential advantages in hardware-limited quantum computers.

Contribution

The paper presents diamond circuits, a novel surface code implementation that reduces qubit and measurement requirements using a mid-cycle, subsystem approach on Lieb lattices.

Findings

Diamond circuits are more qubit- and measurement-efficient than previous surface code constructions.

They preserve the spacelike distance of the code despite reduced qubits.

They may be advantageous in hardware regimes limited by frequency collisions or control lines.

Abstract

We present and benchmark an interesting circuit family which we call diamond circuits, that use a mid-cycle construction built around the subsystem surface code to implement a surface code on a Lieb or "Heavy-Square" lattice. This makes them more qubit- and measurement-efficient than previous constructions. These circuits are described via the LUCI framework, and are effectively circuits with half the measure qubits dropped out of the grid. These circuits preserve the spacelike distance of the code, but suffer a penalty in timelike distance, and could be useful in regimes where quantum computers are limited by frequency collisions or number of control lines.