Measurement-free, scalable, and fault-tolerant universal quantum computing

Science Advances, vol. 11, pp. eadv2590

Abstract

Reliable execution of large-scale quantum algorithms requires robust underlying operations, which is addressed by quantum error correction (QEC). Most modern QEC protocols rely on measurements and feed-forward operations, which are experimentally demanding and often prone to high error rates. Additionally, no single-error-correcting code intrinsically supports the full set of logical operations required for universal quantum computing. In this work, we present a complete toolbox for fault-tolerant universal quantum computing without measurements during algorithm execution by combining the strategies of code switching and concatenation. We develop fault-tolerant, measurement-free protocols to transfer encoded information between 2D and 3D color codes that offer complementary and, in combination, universal sets of robust logical gates. Moreover, we extend the scheme to higher-distance codes by concatenating the 2D color code and integrating code switching for operations lacking a natively fault-tolerant implementation. Our measurement-free approach thereby provides a practical and scalable pathway for universal quantum computing on state-of-the-art quantum processors.

Authors 5

1. Friederike Butt corresponding Aachen Institute for Quantum Information

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute for Quantum Information, RWTH Aachen University, Aachen, Germany

   Institute for Theoretical Nanoelectronics (PGI-2), Forschungszentrum Jülich, Jülich, Germany

2. David F. Locher Aachen Institute for Quantum Information

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute for Quantum Information, RWTH Aachen University, Aachen, Germany

   Institute for Theoretical Nanoelectronics (PGI-2), Forschungszentrum Jülich, Jülich, Germany

3. Katharina Brechtelsbauer

   University of Stuttgart · Center for Integrated Quantum Science and Technology

   Affiliation as printed

   Institute for Theoretical Physics III and Center for Integrated Quantum Science and Technology, University of Stuttgart, Stuttgart, Germany

4. Hans Peter Büchler

   University of Stuttgart · Center for Integrated Quantum Science and Technology

   Affiliation as printed

   Institute for Theoretical Physics III and Center for Integrated Quantum Science and Technology, University of Stuttgart, Stuttgart, Germany

5. Markus Michael Müller Aachen Institute for Quantum Information

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute for Quantum Information, RWTH Aachen University, Aachen, Germany

   Institute for Theoretical Nanoelectronics (PGI-2), Forschungszentrum Jülich, Jülich, Germany