Key Breakthrough for Quantum Computer Reliability – News

Alexandre Blais, Scientific Director of the Department of Quantique (IQ) and Professor of the Department of Physics at the University of Sherbrooke
Photo: Michel Caron – UdeS

By experimentally testing a surface code, a first in quantum error correction, Professor Alexandre Blais and his research group at the Institut quantique de l’UdeS suspected that their progress would mark a turning point in the realization of the quantum computer. Now the prestigious magazine Nature recognizes the importance of this discovery with a scientific publication on 25 May.

Alexandre Blais, Scientific Director of the Department of Quantique (IQ) and Professor of the Department of Physics at the University of Sherbrooke, and his group aim to improve each of the components of this great technology based on superconducting circuits. I 2004, Pr Blais, Steven Girvin, Rob Schoelkopf and Andreas Wallraff have proposed an architecture that makes it possible to imagine the realization of a quantum computer. This approach is now being developed by an ever-growing number of university research groups and companies, including Google, IBM, Amazon and IQ.

Despite the advances made so far, there is a major challenge: Due to the fragility of quantum effects, quantum computers tend to make many more errors than our current computers. Those in the field agree that bug fixes are the next hurdle to overcome to ensure the reliability of these new computers. With their colleagues from ETH Zürich led by Pr Andreas Wallraff, P-groupr Blais, including Élie Genois, Catherine Leroux and Agustin Di Paolo, tackled the problem and the results of their work are set out in an article entitled Realization of repeated quantum error correction in a distance-three surface codetext that the group posted online in December 2021 and which is today published in the prestigious scientific journal Nature.

A significant step towards the realization of the quantum computer

Pr Blais explains that the discovery marks an important milestone:

The first steps were taken by the community, the step we are now taking is essential, namely the completion of several rounds of correction of a surface code, which is considered to be the most promising error-correcting code. This is the first time that it has been possible to implement these theoretical principles in the laboratory on a quantum computer based on superconductors.

Alexandre Blais

The study was conducted with a team from the Swiss Federal Institute of Technology in Zurich (ETH Zurich), who produced this image illustrating the discovery.
The study was conducted with a team from the Swiss Federal Institute of Technology in Zurich (ETH Zurich), who produced this image illustrating the discovery.

Photo: Included

The surface code is an error-correcting code that uses topological characteristics of a network of qubits to protect against errors. Using a superconducting circuit consisting of 17 physical qubits, the team coded quantum information on the device and applied up to 16 rounds of error correction.

The parking teamr Blais worked with Andreas Wallraff’s group at ETH Zurich to achieve these results. The Swiss group performed the experiment, while the group of IQ theorists validated the experimental results using detailed numerical simulations of the experiment.

Élie Genois, doctoral student in the P groupr Blais, explains the challenges of their approach:

Simulating a quantum system of this size is a major challenge. It was therefore necessary to build a model that is capable of giving reasonable results using numerical computer resources that are also reasonable. To model qubits, we have set up a numeric model that allows us to simulate them efficiently. This method provides a lot of information about how the correction code should behave, and it allows us to check if we are able to understand what is happening in the experiment.

Elie Genois, PhD student

The excellent consistency between the numerical simulation of the surface code and the experiment makes it possible to use these simulations to identify the elements that can be refined: “We are now looking to improve operations and achieve better measurement and more control with precise qubits, as this will lead for an even more efficient error correction, which is crucial, as a reliable quantum computer depends on the quality of the physical qubits, ”adds the PhD student.

The next steps

Now that the theoretical and experimental models have been validated, a clearer path emerges for the next steps: “We have not yet reached the point where we can simply scale this architecture, which is still research to be done. But this model guides us towards the next experimental decisions and allows us to see where we need to invest to achieve the greatest gain ”, concludes P.r Blais.

Decades of development were needed to bring the classic computer to market. Pr Blais recalls that the results presented in this study constitute another step leading to the quantum computer: “The quantum computer is not there tomorrow and there is still a lot of work to be done and every step taken brings us closer ‘the goal’ .. Achieving this surface code was a must for the field, ”says the holder of the Rutherford Medal from the Royal Society of Canada in recognition of his achievements.

This development is part of a completely natural timeline: basic research challenges must be solved, all components must be improved, and then you must know how to operate them. These are all challenges for IQ researchers.

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