Contagious error sources would need time travel to prevent quantum computation

TL;DR

This paper introduces a contagious error model in quantum computing that, despite its severity, can be mitigated using quantum teleportation to reduce it to a quasi-independent error model, enabling more robust quantum computation.

Contribution

The paper demonstrates that contagious quantum germs can be effectively managed by converting circuits into bounded quantum depth using quantum teleportation.

Findings

Contagious error sources can be reduced to quasi-independent errors.

Quantum teleportation enables bounded quantum depth circuits.

The approach impacts quantum complexity class considerations.

Abstract

We consider an error model for quantum computing that consists of "contagious quantum germs" that can infect every output qubit when at least one input qubit is infected. Once a germ actively causes error, it continues to cause error indefinitely for every qubit it infects, with arbitrary quantum entanglement and correlation. Although this error model looks much worse than quasi-independent error, we show that it reduces to quasi-independent error with the technique of quantum teleportation. The construction, which was previously described by Knill, is that every quantum circuit can be converted to a mixed circuit with bounded quantum depth. We also consider the restriction of bounded quantum depth from the point of view of quantum complexity classes.