Optimized Surface Code Communication in Superconducting Quantum Computers

TL;DR

This paper compares planar and double-defect surface codes for quantum error correction in superconducting quantum computers, finding that simpler planar codes can outperform more complex codes under certain conditions.

Contribution

It provides a comprehensive analysis of two surface code implementations using full microarchitectural and compiler simulations, revealing new insights into their practical performance.

Findings

Planar codes can outperform double-defect codes in high congestion scenarios.

Simpler surface codes may be more suitable for superconducting quantum computers.

Error correction overhead varies with communication congestion levels.

Abstract

Quantum computing (QC) is at the cusp of a revolution. Machines with 100 quantum bits (qubits) are anticipated to be operational by 2020 [googlemachine,gambetta2015building], and several-hundred-qubit machines are around the corner. Machines of this scale have the capacity to demonstrate quantum supremacy, the tipping point where QC is faster than the fastest classical alternative for a particular problem. Because error correction techniques will be central to QC and will be the most expensive component of quantum computation, choosing the lowest-overhead error correction scheme is critical to overall QC success. This paper evaluates two established quantum error correction codes---planar and double-defect surface codes---using a set of compilation, scheduling and network simulation tools. In considering scalable methods for optimizing both codes, we do so in the context of a full microarchitectural and compiler analysis. Contrary to previous predictions, we find that the simpler planar codes are sometimes more favorable for implementation on superconducting quantum computers, especially under conditions of high communication congestion.