A research paper published in 2012 by Matteo Mariantoni, a professor in the department of Physics and Astronomy, appeared on the Physical Review A 50th Anniversary Milestones list.
The prestigious journal is celebrating its fiftieth anniversary with a list of papers that have made important contributions to the various areas of physics under its purview.
The article Surface codes: Towards practical large-scale quantum computation, co-authored by Mariantoni in 2012, explained a new, more accessible approach to quantum error correction to the quantum information community and provided an early estimate of the infrastructure requirements for a practical quantum computer based on this approach.
The article went on to be cited more than a thousand times.
“When we wrote the article, I never expected it to be so impactful,” said Mariantoni. “It became a reference guide on quantum error correction and the difficulty of building a practical quantum computer for the quantum information community.”
The paper was also the beginning of the spread of quantum computing research from the lab to industry. “It served as a catalyst for many companies like Google and IBM to invest in quantum computing in a big way because there was this new positive thing to work on,” said Mariantoni.
Ironically, this paper that has impacted so many researchers began as an internal report. The Martinis-Cleland research group, where Mariantoni was a postdoc, was trying to understand what appeared to be a very promising paper on quantum error correction published by mathematicians Raussendorf and Harrington in 2007. At the time, Raussendorf was working from the Perimeter Institute in Waterloo, Ontario.
The team spent about nine months interpreting the article and translating its complicated mathematical language into something practical for experimental physicists. When they began to present their work at various events and saw the enthusiasm of their audiences, they knew they had something worth submitting for publication.
The rest is history.
While Mariantoni was at the University of California, Santa Barbara at the time of the publication, the work has influenced his research path ever since. “This article helped me realize what I should focus on for the past decade,” said Mariantoni.
The paper’s two key insights provided a bittersweet revelation for researchers looking to build the first practical quantum computer.
On the one hand, they now had a more accessible approach to quantum error correction that would allow them to begin working right away with hardware they already had. On the other hand, they now saw this approach would need an unfathomable number of qubits—at least half a billion—to result in a practical error-corrected quantum computer.
For Mariantoni, this dual revelation suggested a research path; maybe the hardware itself can be improved enough to reduce the number and intractability of quantum errors so that quantum error correction and useful computation will be possible with a more practical number of qubits.
Now, Mariantoni and his team are working on a completely new approach to “outsmart” errors using photonic band-gap engineering.
“We are trying to combine many techniques which we know about superconducting devices to make them better, not even to remove these errors, but to make them better errors,” said Mariantoni.
Quantum errors still stand as a looming obstacle to practical quantum computing, but this seminal work on the surface code approach to quantum error correction shows what was possible and what is currently beyond reach, serving as a guidepost for thousands of researchers in the decade since.