Conventional information science implicitly assumes that all information processing devices are governed by classical mechanics. However, recent integrated circuits are so small that it is impossible to explain their behavior without quantum mechanics. Hence, we study quantum information science which aims to develop revolutionary software by utilizing quantumness of information processing devices.
Until now, various kind of quantum information processing have been developed; e.g. quantum key distribution that is unconditionally secure as long as quantum mechanics is correct, quantum algorithm that is exponentially faster than existing algorithm, quantum channel coding that exceeds Shannon bounds of information theory, .. etc. These researches of quantum information science showed that quantum correlation called entanglement is essential for a quantum information processing outperforms conventional information processing. Our group study quantification and certification of entanglement as well as various quantum information processing utilizing entanglement.
A quantum network consists of many separated quantum computers connected by quantum channels. By a quantum network, we can implement various quantum information processing which cannot be implemented by a stand-alone quantum computer; e.g. quantum distributed computation, quantum money, quantum cloud computation,.. etc. Our group study various information processing on quantum networks.
Toward practical realization of quantum computers
At present, quantum computers developed in labs have only 1-10 bits, and are far from practical applications. In order to their practical realization, we need farther innovation in developed technology of quantum electronics. However, no one know when such innovation is realized. Hence, our group intends to accelerate practical realization of quantum computers by means of study in theoretical information science. For example, we are developing a new solution for the problem of decoherence in quantum devices, and studying who to control whole quantum system by only accessing a part of it.