Quantum circuit complexity research NISHINO Lab, Tokyo University of Electro-communications This ATIP report summarizes the recent site visit to the laboratory of theoretical computer scientist Tetsuro NISHINO, of The University of Electro-communications, Tokyo on 14 November 2003. Dr. NISHINO’s research focuses upon quantum computation, neural networks, and circuit complexity theory. Keywords Quantum computation, cryptography, neural networks, circuit complexity 1. EXECUTIVE SUMMARY • NISHINO’s work in NMR (nuclear magnetic resonance)-based bulk quantum computation has identified key differences in contrast to standard quantum Turing machines and defined advantages over Grover’s search against secret-key cryptosystems • NISHINO is performing quantum computing simulations to minimize quantum circuit complexity for any given Boolean function and has introduced a recurrent network model for the implementation of quantum neural networks • NISHINO has demonstrated that a single-layer quantum perceptron can solve the XOR problem, a task impossible for classical perceptrons, and hopes to study the properties of quantum neural networks in both NMR and coherent photonics-based quantum computers Impact & Assessment Japanese progress in quantum algorithms research is underrepresented in contrast to its well-established position as a leader in quantum computing hardware development. The Soumu-sho Roadmap on Japan’s strategy for the realization of quantum information and communications technologies has added two quantum information scientists to its roster: Dr. Hideki IMAI (The University of Tokyo) and Dr. Osamu HIROTA (Tamagawa Gaku-en University). They are expected to increase the national emphasis upon quantum information theory. Dr. Tetsuo NISHINO and Dr. Kazuo IWAMA (Kyoto University) are two of the foremost Japanese researchers in Christopher Altman Quantum Information Science and Technology Project