The paradigm shift in quantum physics, which has unfolded since the early 1980's, has culminated in the development of quantum information, by integrating the cutting-edge technologies in optical and solid-state devices. In parallel with this, laser cooling and related technologies for manipulating atoms have led to the creation of gaseous Bose-Einstein condensates, which have enabled us to study macroscopic quantum many-body systems with unprecedented precision, and produced several ground-breaking achievements. More recently, techniques to manipulate and probe quantum many-body systems at the level of single atoms and also precision control of few-body systems have seen remarkable progress. In this article, some recent topics of ultracold atoms and related studies are reviewed.

In this paper, we review the fundamentals of a macroscopic coherence of semiconductor quantum dots and its applications, to a quantum interface. A macroscopic coherence of a large number of semiconductor quantum dots generated using resonant ultrafast pulses plays an important role in a light-matter quantum interface. A photon-echo technique can recover the inhomogeneous dephasing of macroscopic coherence caused by the inhomogeneous distribution of resonant frequencies of excitons in a quantum dot ensemble. As a result, the photon-echo technique enables us to realize a quantum interface between single photon pulses and an inhomogeneous two-level system.

Optomechanics is an emerging field that exploits parametric interaction between electromagnetic fields and mechanical oscillators. This coupling enables us to freeze out vibrational modes of the oscillator toward its quantum ground state, to coherently transfer quantum states between different degrees of freedom, and to measure the oscillator's displacement at or below the standard quantum limit. We are about to explore a truly quantum regime of mechanical control over a wide range of oscillator sizes. This article introduces a part of the rapidly progressing experiments in terms of the basic mechanism of the photon-phonon coupling and sideband cooling method.

The development of small and scalable solid state quantum systems, where quantum manipulations are possible, is essential for quantum information science. However, unlike a trapped atom system, it is very difficult to isolate a solid state quantum system from thermal disturbances. Cryogenic technology and nanofabrication technology make a mechanical oscillator a likely candidate for a new solid state quantum system. It has been possible to cool mesoscale oscillators down to the quantum ground state using radiation pressure. In this article, the physics of laser cooling of mechanical oscillators with photonic crystal nanocavities is introduced with the future prospects of this field.

Detection of a weak magnetic field with high spatial resolution is an important technique, which enables various applications in a wide range of fields, from fundamental physics to medical technology. We address the realization of this technique by using atomic gaseous Bose-Einstein condensates with internal spin degrees of freedom. Here, we describe the latest research developments in our group, especially for the detection of alternate-current magnetic fields using a spin-echo-based magnetometer.

In several kinds of dilute atomic gases, Bose-Einstein condensates with almost no thermal atoms have been created using laser cooling techniques. The dynamics of the condensate, which are observed directly with optical means, are well described with a condensate wave function. In this paper, we report our experimental study on phase manipulation for the condensate wave function with electromagnetic fields or laser beams. It enables new experiments on superfluidity and novel applications using matter waves. As an example, we introduce our experiment on the creation of a multiply-charged quantized vortex.

It has become possible to laser cool mechanical oscillators, i.e., massive macroscopic objects, just like atomic gases and ions in a vacuum. In this article we aim at understanding the way in which Brownian motion of mechanical oscillators can be cooled with a laser and a cavity by simple and phenomenological classical arguments. Equipped with the classical model we present the first photo-thermal-effect-based cavity cooling experiment of a metal-coated cantilever, our cavity cooling experiment with a semiconductor nanomembrane, and radiation-pressure-based cavity cooling experiments.

We discuss the characteristics of graphene, which is expected to become a new transparent electrode material, in comparison with ITO.

The synthesis methods of graphene, which are indispensable for industrial use are overviewed. The attempts at mass production of graphene by roll-to-roll synthesis, and the roadmap for the development of graphene transparent electrode are discussed.