A road for realizing practical quantum computers

−Lying bottlenecks on the road and recent developments toward the realization using photons−

Abstract

Scalability, expandability and fault tolerance are requirements for the realization of practical quantum computers that have a computation ability superior to present super computers. Such concepts are summarized to clarify the bottlenecks in the realization of the quantum computers. Recent experiments on quantum computers are reviewed with our recent report on a development in photonic quantum information processing.