New Superconducting Circuit Could Accelerate Realization of Fault-Tolerant Quantum Computer


Results from research conducted with RWTH members published in scientific journal "Physical Review X".


RWTH researchers, together with colleagues from the University of Basel and TU Delft, have now designed a superconducting circuit that could accelerate the realization of a fault-tolerant quantum computer. Professor David DiVincenzo and Martin Rymarz from the RWTH Chair of Theoretical Physics were involved in this project. DiVincenzo is also director of the JARA Institute for Quantum Information and the Institute for Theoretical Nanoelectronics at Forschungszentrum Jülich. They both also conduct research in the Matter and Light for Quantum Information (ML4Q) Cluster of Excellence.

Building a universal quantum computer is a challenging endeavor due to the susceptibility of failure of quantum bits, or qubits. To contain this problem, quantum error-correcting (QEC) codes that can reliably encode quantum information have been developed. Conventional QEC codes do this by combining multiple imperfect qubits to encode a logical qubit that offers improved features and better performance. Such codes are usually based on complicated active protocols that require a great hardware investment. The new strategy bypasses the need for active stabilization and promises the desired benefits of QEC codes in a manner that is highly efficient when it comes to hardware usage. This built-in feature thus encodes a qubit that is inherently protected against environmental interference yet controllable, making it a competitive contender for a qubit of future large-scale quantum processors.

"By implementing a gyrator – a two-terminal electrical device that couples current at one terminal with voltage at the other – between two superconducting devices (called Josephson junctions), we could eliminate the need for active fault detection and stabilization. When the qubit is cooled, it is inherently protected against common types of noise," Rymarz explains. He is first author of the article "Hardware-Encoding Grid States in a Non-Reciprocal Superconducting Circuit", now published in Physical Review X, which presents the research results.

The research was carried out as part of the Matter and Light for Quantum Information (ML4Q) Cluster of Excellence. One of the goals of ML4Q is to develop advanced error correction schemes and test them experimentally via four focus areas and collaborations with experimental groups, and apply them to the physical platforms being designed in other focus areas of the Cluster.

"I hope our work will inspire efforts in the lab. I realize that, like many of our proposals, this may be a little ahead of its time," DiVincenzo said. "Given the technical expertise in ML4Q's experimental groups, we see the possibility of testing our proposal in the laboratory in the foreseeable future.”

The Matter and Light for Quantum Information (ML4Q) Cluster of Excellence

ML4Q is a research network of the University of Cologne, the University of Bonn, RWTH, and Forschungszentrum Jülich that has been funded as part of the Excellence Strategy, a funding program of the German federal and state governments since 2019. The Cluster of Excellence aims to create new computer and network architectures based on the principles of quantum mechanics. Quantum computers promise computing power that exceeds that of all conventional computers, for example materials research, pharmaceuticals, or artificial intelligence. Quantum communication is tap-proof and can be encrypted and can thus help in implementing secure communication networks. ML4Q combines the expertise of the partners in three key physics disciplines: solid state research, quantum optics, and quantum information to create the best hardware platform for quantum information technology and blueprints for a functional quantum information network.


Hardware-Encoding Grid States in a Nonreciprocal Superconducting Circuit. Martin Rymarz, Stefano Bosco, Alessandro Ciani, David P. DiVincenzo. Phys Rev X 2021. DOI 10.1103/PhysRevX.11.011032

Source: Press and Communications