Quantum Information Processing manuscript No. (will be inserted by the editor) The quest for a Quantum Neural Network Maria Schuld · Ilya Sinayskiy · Francesco Petruccione Received: date / Accepted: date Abstract With the overwhelming success in the field of quantum information in the last decades, the ‘quest’ for a Quantum Neural Network (QNN) model began in or- der to combine quantum computing with the striking properties of neural computing. This article presents a systematic approach to QNN research, which so far consists of a conglomeration of ideas and proposals. It outlines the challenge of combining the nonlinear, dissipative dynamics of neural computing and the linear, unitary dy- namics of quantum computing. It establishes requirements for a meaningful QNN and reviews existing literature against these requirements. It is found that none of the proposals for a potential QNN model fully exploits both the advantages of quantum physics and computing in neural networks. An outlook on possible ways forward is given, emphasizing the idea of Open Quantum Neural Networks based on dissipative quantum computing. Keywords Quantum Computing · Artificial Neural Networks · Open Quantum Systems · Quantum Neural Networks 1 Introduction Quantum Neural Networks (QNNs) are models, systems or devices that combine features of quantum theory with the properties of neural networks. Neural networks M. Schuld Quantum Research Group, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, KwaZulu-Natal, 4001, South Africa E-mail:
[email protected] I. Sinayskiy Quantum Research Group, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, KwaZulu-Natal, 4001, South Africa and National Institute for Theoretical Physics (NITheP), KwaZulu-Natal, 4001, South Africa F.