Several techniques are utilized to correct errors in quantum computers. However, different correction codes do not perform equally well for all types of operations. To address this challenge, a research group from the University of Innsbruck has collaborated with researchers from RWTH Aachen and the Forschungszentrum Jülich to develop a novel method that they have successfully implemented for the first time. This innovative approach enables a quantum computer to switch between two correction codes, ensuring that all computational tasks are protected from errors.
Like all computers, quantum computers can experience errors. Usually, these errors are mitigated using various technical solutions or are detected and corrected during the computation process. The challenge in quantum computing is intensified because it is impossible to duplicate an unknown quantum state. This means that it cannot be replicated throughout the calculations, making it challenging to identify errors by comparing multiple copies. Inspired by classical computing, quantum physics has developed a method to distribute quantum information across multiple entangled quantum bits, ensuring redundancy. This approach relies on what are known as correction codes to define its specifics.
In 2022, a group led by Thomas Monz from the University of Innsbruck’s Department of Experimental Physics, along with Markus Müller from RWTH Aachen’s Department of Quantum Information and the Peter Grünberg Institute at Forschungszentrum Jülich, achieved a significant breakthrough. They showcased a universal set of operations on fault-tolerant quantum bits, revealing how quantum algorithms could be designed to correct errors efficiently. However, different quantum error correction codes come with their unique set of challenges. There is a theorem stating that no single correction code can easily manage all gate operations needed for flexible computations with logical quantum bits while still ensuring error protection.
Implementing quantum gates with varying correction codes
To tackle this problem, Markus Müller’s team has developed a technique that allows the quantum computer to seamlessly transition between two correction codes while maintaining error tolerance. “This functionality helps the quantum system to switch to the second code when it encounters a logic gate that is difficult to implement with the first code. This adaptability simplifies the realization of all essential gates for computation,” explains Friederike Butt, a PhD student in Müller’s group. She was responsible for designing the quantum circuits for their experiment, working closely with Thomas Monz’s research team in Innsbruck. “Together, we successfully achieved the complete implementation of a full set of quantum gates on an ion trap quantum computer using a combination of two quantum error correction codes,” shares Ivan Pogorelov, a PhD candidate from the Innsbruck team.
“This accomplishment is the result of our long-standing and productive collaboration with Markus Müller’s team,” notes Thomas Monz, who has known the theoretical physicist since his doctoral studies at the University of Innsbruck.
The findings of this research were published in the journal Nature Physics. The study was financially supported by various organizations, including 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.
