# Large-scale quantum computing with quantum teleportation

A new era of quantum technologies with ground breaking capabilities is emerging. The global race to build quantum computers is heating up. Around the world, governments and corporations are accelerating their investments in science and engineering research for quantum computers, quantum communications systems, and other quantum technologies. Supremacy in quantum science and technology is recognised as critical for national security and economic growth into the future. A ‘quantum race’ is upon us.

The present digital age resulted from the application of quantum science and engineering to create the transistor microchips that power the computers and smart phones we use every day. This first quantum revolution exploited physical characteristics of semiconductor materials. Now, the emerging second quantum revolution is engineering radically new machines that exploit information theory and computer science. By engineering quantum mechanics in novel ways, quantum computers can perform calculations much faster than any conventional machine, and allow for perfectly secure communications.

Professor Furusawa is one of the world’s leading quantum scientists. His pioneering work on quantum optical teleportation is now revolutionising the development of quantum computers. In this Public Lecture, Professor Furusawa will describe how teleportation is being used to enable a new generation of large-scale quantum computer experiments.

Quantum teleportation is the transfer of fully quantum information – impossible by conventional means. In conventional communication systems, copying information is possible. However, it is not allowed in quantum mechanics. The only way allowed in quantum mechanics is that input information disappears at the sending station and reappears at the receiving station. This is the nature of quantum teleportation. For quantum teleportation, we need quantum entanglement, which is what Albert Einstein called “spooky” action at a distance. Two-party quantum entanglement is a superposition of all possible states, where the measurement of one side affects the state at the other side even when they are spatially separated. We use this “spooky” action for quantum teleportation.

For large-scale quantum computing, we use a class of multipartite entangled states, called “cluster states”. The cluster state is a superposition of all possible quantum computing patterns. We can select a desired quantum computing pattern by using measurements. Similar to quantum teleportation, we can eliminate the randomness of measurement results by using “feedforward” control. In that sense, large-scale quantum computing can be regarded as sequential quantum teleportation. We have already succeeded in creation of such cluster states for large-scale quantum computing in our laboratory in Tokyo.

## Biography

Professor Akira Furusawa received his Ms Degree in applied physics and Ph.D. Degree in physical chemistry from The University of Tokyo, Japan, in 1986, and 1991, respectively. His research interests cover the area of nonlinear optics, quantum optics and quantum information science. Professor Furusawa has authored more than 100 papers in leading technical journals and conferences, which include the first realizations of continuous-variable quantum teleportation (A. Furusawa et al, Science 282, 706 (1998)), quantum teleportation network (H. Yonezawa et al., Nature 431, 430 (2004)), generation of nine-party quantum entanglement and its application to quantum error correction (T. Aoki et al., Nature Physics 5, 541 (2009)), quantum teleportation of Schrödinger’s cat state (N. Lee et al., Science 332, 330 (2011)), adaptive homodyne measurement in the non-classical level (H. Yonezawa et al., Science 337, 1514 (2012)), deterministic quantum teleportation of optical qubits (S. Takeda et al., Nature 500, 315 (2013)), generation of 10000-wavepacket quantum entanglement or CV cluster state for large-scale quantum computing (S. Yokoyama et al., Nature Photonics 7, 982 (2013)), generation and verification of CV quantum entanglement on a chip (G. Masada et al., Nature Photonics 9, 316 (2015)), and synchronization of two quantum optical memories (K. Makino et al., Science Advances 2, e1501772 (2016)). Professor Furusawa received the Ryogo Kubo Memorial Award in 2006, the JSPS Prize and the Japan Academy Medal in 2007, the International Quantum Communication Award in 2008, the Palacky University Medal in 2011, the Toray Science and Technology Prize in 2015, and the Medal with Purple Ribbon in 2016.