Quantum Computers Just Got Smarter With Dual-Code Error Correction
A team of physicists has introduced an innovative error-correction method for quantum computers, enabling them to switch error correction codes on-the-fly to manage complex computations more effectively and with fewer errors.
Error Correction in Quantum Computing
Computers can make mistakes, but in classical systems, these errors are usually detected and corrected using various technical methods. Quantum computers, however, face a unique challenge — quantum states cannot be copied. This limitation means that errors cannot be identified by comparing multiple saved copies, as is done in classical computing.
To overcome this, quantum physicists have drawn inspiration from classical error correction techniques and developed a different approach. In quantum systems, information is spread across several entangled quantum bits (qubits), creating redundancy to help detect and correct errors. This process is guided by specific frameworks known as quantum error correction codes.
In 2022, a research team led by Thomas Monz from the University of Innsbruck and Markus Müller from RWTH Aachen and the Peter Grünberg Institute at Forschungszentrum Jülich successfully implemented a universal set of operations on fault-tolerant quantum bits. Their achievement demonstrated how quantum algorithms can be designed to efficiently correct errors during computation.
Despite this progress, implementing quantum error correction is not without its challenges. A fundamental theorem in quantum computing states that no single correction code can perform all the gate operations needed for fully programmable computations in a way that is both error-protected and efficient.
Innovations in Quantum Codes
To circumvent this difficulty, Markus Müller’s research group has established a method that allows the quantum computer to switch back and forth between two correction codes in an error-tolerant manner.
“In this way, the quantum computer can switch to the second code whenever a logic gate that is difficult to realize appears in the first code. This makes it easier to implement all the gates required for computing,” explains Friederike Butt, a doctoral student in Markus Müller’s research group.
She developed the quantum circuits on which the experiment is based and implemented them in close collaboration with Thomas Monz’s research group in Innsbruck.
“Together, we have succeeded for the first time in realizing a universal set of quantum gates on an ion trap quantum computer using two combined quantum error correction codes,” says PhD student Ivan Pogorelov from the Innsbruck research group.
“This result is based on our many years of good collaboration with Markus Müller’s team,” says Thomas Monz, who knows the theoretical physicist from his doctoral studies at the University of Innsbruck.
The findings of the current study were published in the journal Nature Physics.
Reference: “Experimental fault-tolerant code switching” by Ivan Pogorelov, Friederike Butt, Lukas Postler, Christian D. Marciniak, Philipp Schindler, Markus Müller and Thomas Monz, 24 January 2025, Nature Physics.
DOI: 10.1038/s41567-024-02727-2
The research was financially supported among others by the Austrian Science Fund FWF, the Austrian Research Promotion Agency FFG, the German DFG, the Bavarian State Government, the European Union and the Federation of Austrian Industries Tyrol.