Realization of a quantum neural network using repeat-until-success circuits in a superconducting quantum processor

• Published in: npj quantum information Vol. 9; no. 1; pp. 118 - 7
• Main Authors: Moreira, M. S., Guerreschi, G. G., Vlothuizen, W., Marques, J. F., van Straten, J., Premaratne, S. P., Zou, X., Ali, H., Muthusubramanian, N., Zachariadis, C., van Someren, J., Beekman, M., Haider, N., Bruno, A., Almudever, C. G., Matsuura, A. Y., DiCarlo, L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.11.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/483/2802; 639/766/483/481; Algorithms; Boolean; Circuits; Classical and Quantum Gravitation; Deep learning; Neural networks; Neurons; Optimization; Physics; Physics and Astronomy; Quantum Computing; Quantum Field Theories; Quantum Information Technology; Quantum Physics; Relativity Theory; Spintronics; String Theory; Success
• ISSN: 2056-6387; 2056-6387
• DOI: 10.1038/s41534-023-00779-5

Artificial neural networks are becoming an integral part of digital solutions to complex problems. However, employing neural networks on quantum processors faces challenges related to the implementation of non-linear functions using quantum circuits. In this paper, we use repeat-until-success circuits enabled by real-time control-flow feedback to realize quantum neurons with non-linear activation functions. These neurons constitute elementary building blocks that can be arranged in a variety of layouts to carry out deep learning tasks quantum coherently. As an example, we construct a minimal feedforward quantum neural network capable of learning all 2-to-1-bit Boolean functions by optimization of network activation parameters within the supervised-learning paradigm. This model is shown to perform non-linear classification and effectively learns from multiple copies of a single training state consisting of the maximal superposition of all inputs.