Student’s homework picked up by Amazon

Student’s homework picked up by Amazon Pablo Bonilla Ataides (left) with co-author Dr Ben Brown from the School of Physics. Credit: Louise Cooper

University of Sydney science undergraduate Pablo Bonilla Ataides has tweaked some computing code to effectively double its capacity to correct errors in the quantum computers. This homework has attracted the attention of quantum computing programmers at Amazon Web Services and Yale University.

Performing large calculations with a quantum computer will likely require a fault-tolerant architecture based on quantum error-correcting codes. The challenge is to design practical quantum error-correcting codes that perform well against realistic noise using modest resources. The student showed that a variant of the surface code—the XZZX code—offers remarkable performance for fault-tolerant quantum computation.

The error threshold of this code matches what can be achieved with random codes (hashing) for every single-qubit Pauli noise channel; it is the first explicit code shown to have this universal property.

He presented numerical evidence that the threshold even exceeds this hashing bound for an experimentally relevant range of noise parameters. Focusing on the common situation where qubit dephasing is the dominant noise, he showed that this code has a practical, high-performance decoder and surpasses all previously known thresholds in the realistic setting where syndrome measurements are unreliable.

He went on to demonstrate the favorable sub-threshold resource scaling that can be obtained by specializing a code to exploit structure in the noise. He also showed that it is possible to maintain all of these advantages when he performed fault-tolerant quantum computation.

The XZZX surface code.
The XZZX surface code.

The results of the study, co-authored by Dr. Steve Flammia who has recently moved from the University of Sydney to AWS’s quantum computing effort, are to feature in the tech company’s arsenal of error correction techniques as it develops its quantum hardware. (

The research has been published in Nature Communications.

Read more.