Achieving fault tolerance against amplitude-damping noise

TL;DR

This paper develops a fault-tolerant quantum computing protocol specifically designed for amplitude-damping noise, demonstrating the potential for targeted noise model approaches to improve quantum computation accuracy.

Contribution

It introduces a 4-qubit code and recovery procedure tailored for amplitude-damping noise, expanding fault tolerance strategies beyond traditional Pauli noise models.

Findings

Computed the pseudothreshold for amplitude-damping noise

Demonstrated the feasibility of targeted noise-specific fault tolerance

Showed limitations of standard fault tolerance intuition under non-Pauli noise

Abstract

With the intense interest in small, noisy quantum computing devices comes the push for larger, more accurate -- and hence more useful -- quantum computers. While fully fault-tolerant quantum computers are, in principle, capable of achieving arbitrarily accurate calculations using devices subjected to general noise, they require immense resources far beyond our current reach. An intermediate step would be to construct quantum computers of limited accuracy enhanced by lower-level, and hence lower-cost, noise-removal techniques. This is the motivation for our work, which looks into fault-tolerant encoded quantum computation targeted at the dominant noise afflicting the quantum device. Specifically, we develop a protocol for fault-tolerant encoded quantum computing components in the presence of amplitude-damping noise, using a 4-qubit code and a recovery procedure tailored to such noise. We describe a universal set of fault-tolerant encoded gadgets and compute the pseudothreshold for the noise, below which our scheme leads to more accurate computation. Our work demonstrates the possibility of applying the ideas of quantum fault tolerance to targeted noise models, generalizing the recent pursuit of biased-noise fault tolerance beyond the usual Pauli noise models. We also illustrate how certain aspects of the standard fault tolerance intuition, largely acquired through Pauli-noise considerations, can fail in the face of more general noise.