Success in Error Correction Marks Breakthrough in Quantum Computing


An international research team involving the Theoretical Quantum Technology Group at RWTH Aachen University succeeded in implementing quick and continuous quantum error correction in digital quantum systems.


Researchers from ETH Zurich, supported by RWTH’s Theoretical Quantum Technology Group, Forschungszentrum Jülich, and researchers from Canada, succeeded for the first time in implementing quick and continuous quantum error correction in digital quantum systems. With this work, published in Nature, the researchers have cleared an important hurdle on the path to practical quantum computing.

“Building practical quantum computers critically depends on the ability to detect and correct errors on quantum bits (qubits) quickly enough and repeatedly before they pile up and lead to failures in quantum computations," explains Professor Markus Müller, whose research group at the RWTH Institute for Quantum Information and at the Peter Gruenberg Institute at Forschungszentrum Jülich explores protocols for quantum computing and error correction.

The System Is Capable of Detecting and Correcting Errors

Previous error correction methods have been unable to simultaneously detect and correct both of the fundamental types of error that occur in quantum systems. A team led by Professor Andreas Wallraff at ETH Zurich has now presented the first system that is able to repeatedly detect and correct both types of errors. The researchers achieved this important success with the help of a chip that features a total of 17 superconducting qubits and is operated at a temperature of just 0.01 Kelvin, barely above absolute zero.

The research team performed the error correction using a so-called surface code – a method which distributes the quantum information of a qubit among several physical qubits. Nine of the chip's 17 qubits are arranged in a square three-by-three array and together form what is known as a logical qubit: the computational unit of a quantum computer. The remaining eight qubits on the chip serve as auxiliary qubits; they serve to detect errors in the system.

If a disturbance occurring in the logical qubit corrupts the information, the system recognizes this disturbance as an error. This information is obtained by repeatedly and rapidly measuring the eight auxiliary qubits. This information can then be used to deduce what type of error most likely occurred and where on the chip it occurred without disturbing the quantum information stored in the logical qubit. To remedy the effect of the detected errors, it is possible to make suitable corrections to the qubits. Alternatively, for most applications, including the present experiment, it is sufficient to keep track of the detected errors and correct them after completion of the quantum computation.

RWTH and Forschungszentrum Jülich are involved in a number of research consortia aiming to build practical quantum computers based on several promising physical platforms, including those using trapped ions (AQTION, IQuAn), neutral atoms (MUNIQC-Atoms) and superconducting qubits (OpenSuperQ, QSolid). “The experiments performed by our colleagues at ETH Zurich are impressive and demonstrate the potential of quantum error correction techniques to protect quantum processors from glitches,” says Müller. “It is expected that larger devices currently under development will require more complex technology. But – when equipped with error-correction protocols – they will eventually provide even greater protection from errors.”

Publication: Krinner, S. et al.: Realizing Repeated Quantum Error Correction in a Distance-Three Surface Code (Nature 2022)