Quantum computers and quantum annealing machines are promising for efficiently solving mathematical problems that are currently intractable by exploiting quantum mechanical principles. Recently, rapid developments based on superconducting quantum electronics have been made in a technology for such quantum machines. In addition, big IT companies such as Google, IBM, Intel, and Microsoft are now investing heavily in this quantum technology. In this article, we will discuss recent developments in quantum computers and quantum annealing machines.
Research towards the realization of superconducting quantum computers is progressing rapidly. Recently, the number of integrated quantum bits (qubits) has begun to exceed 50 bits, and such quantum system has the potential capability to surpass that of any classical computer (quantum supremacy). To improve gate fidelity, research on qubits and surrounding environments are actively being studied. Which superconducting circuit will become the platform for quantum computers? What kind of technologies and theory will be used for quantum computers? In this paper, we cover many issues leading towards the realization of quantum computing systems.
Quantum annealing (QA) is a promising calculation method for obtaining a better solution to combinatorial optimization problems. QA is a natural computation technique proposed in the context of statistical physics in 1998. In 2011, the world's first commercial machine realizing QA experimentally was released. After that, the development of hardware and software has been exhaustive, and the studies on application search have been done using commercial QA machines. In this paper, we first explain the basics of QA without assuming the knowledge of statistical physics and quantum physics. We also show a couple of examples of application studies on QA. In addition, existing problems and overcoming other methods are explained.