Fight or Flight: Cosmic Ray-Induced Phonons and the Quantum Surface Code

TL;DR

This paper proposes a hybrid hardware-software strategy using the surface code to mitigate cosmic ray-induced errors in quantum computers by relocating logical qubits away from error epicenters, significantly reducing data loss.

Contribution

It introduces a novel approach of moving logical qubits to avoid cosmic ray errors, detailing hardware requirements, qubit mapping, and code distance considerations.

Findings

Reduces logical qubit failure probability from 100% to 4-15%.

Analyzes cosmic ray events near and far from surface code holes.

Provides a practical framework for implementing qubit relocation.

Abstract

Recent work has identified cosmic ray events as an error source limiting the lifetime of quantum data. These errors are correlated and affect a large number of qubits, leading to the loss of data across a quantum chip. Previous works attempting to address the problem in hardware or by building distributed systems still have limitations. We approach the problem from a different perspective, developing a new hybrid hardware-software-based strategy based on the 2-D surface code, assuming the parallel development of a hardware strategy that limits the phonon propagation radius. We propose to flee the area: move the logical qubits far enough away from the strike's epicenter to maintain our logical information. Specifically, we: (1) establish the minimum hardware requirements needed for our approach; (2) propose a mapping for moving logical qubits; and (3) evaluate the possible choice of the code distance. Our analysis considers two possible cosmic ray events: those far from both ``holes'' in the surface code and those near or overlapping a hole. We show that the probability that the logical qubit will be destroyed can be reduced from 100% to the range 4% to 15% depending on the time required to move the logical qubit.