Robust quantum error correction (QEC) is a necessary ingredient for achieving practical quantum computing and as you might expect there’s an abundance of ongoing work in the area. Recently, separate teams of researchers reported progress in demonstrating not only error detection but also error correction using so-called surface codes. This is a first for surface codes.
There’s a short, excellent account of the work (Error-Correcting Surface Codes Get Experimental Vetting) written by Luigi Frunzio and Shraddha Singh and posted today on the APS physics website.
As explained by the authors, “These codes are promising because they are experimentally straightforward to implement and because, under certain conditions, they can tolerate relatively large error rates. But until now, demonstrations with the surface code have only detected errors, not corrected them. Now, two groups, led by Jian-Wei Pan at the University of Science and Technology of China in Hefei and Andreas Wallraff at the Swiss Federal Institute of Technology (ETH) in Zurich, have achieved the first-ever demonstration of error correction with surface codes. These results bring us a step closer toward realizing a practical quantum computer.”
Both groups have recently published papers on their work: Y. Zhao et al., “Realization of an error-correcting surface code with superconducting qubits,” Phys. Rev. Lett.129, 030501 (2022); Krinner et al., “Realizing repeated quantum error correction in a distance-three surface code,” Nature 605, 669 (2022).
The brief Frunzio-Singh article is a succinct overview of the recent work and also of quantum error correction.
QEC schemes involve redundantly encoding quantum information of a single “logical” qubit in a many-body entangled state of multiple “physical” qubits so that comparisons between these qubits reveal if one or more of them has changed. “The number of physical qubits used to encode a logical qubit is called the distance of the code, and a code gets exponentially better at suppressing logical errors as the distance increases (at the cost of increased hardware complexity),” wrote Frunzio and Singh.
With surface codes the connections between elements of the quantum computer can be visualized as forming a 2D checkerboard pattern. Pan’s and Wallraff’s groups are the first to successfully implement the smallest (with a distance of three) error-correcting surface code.
Link to APS article, https://physics.aps.org/articles/v15/103
Link to Zhao paper, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.030501
Link to Krinner paper, https://www.nature.com/articles/s41586-022-04566-8