The recent progress of the hardware of the quantum computer are dramatic, and quantum computers with several hundreds of qubits might be within reach in a few years. This progress is motivating the world to search for applications of such devices. Here we give the overview of the recent development of algorithms for near-term, noisy quantum computers. This article is focused especially on so-called variational quantum algorithms where classical and quantum computers works together to solve a given task. The near-term quantum computers are expected to be applied in the area ranging from machine learning to quantum chemistry calculation. We also review some of the approaches to mitigate the noise effect.
Liquids can be easily deformed with respect to a shape of container, and believed that the transverse phonons cannot exist owing to the lack of restoring shear forces. If liquids are observed in pico-second and nano-meter scales, however, they have a solid-like behavior of the so-called cage effect. Developments of high energy resolution inelastic x-ray scattering (IXS) techniques enable one to find transverse phonon excitations in simple liquid metals and Peierls-like instabilities in the dispersion relation of the acoustic phonon excitations. Recent IXS experiments on liquids are reviewed in this article to show that nano-scale three-dimensional atomic structures in liquid are highly correlated to the liquid natures.
Properties of covalent liquids under high pressures have been investigated by means of ab initio molecular dynamics simulations. From our simulation, it is found that liquid B2O3 has anomalous diffusion properties under high pressure. We clarified atomic diffusion mechanisms which are origins of the anomalous diffusion properties. We have also investigated metallization of liquid Se under high pressure. Our simulation revealed that a covalentlike interaction exists even in the metallic state of liquid Se, which gives a singular feature of the static structure in metallic state of liquid Se. In addition to these liquids, we have investigated atomic diffusion in basaltic melt under pressure and discussed the mechanism of accumulation in interior of the Earth, in which seismic discontinuity is observed.
Recently, the diffusion processes in a cell were observed by direct tracking of particles inside a cell. The experimental results imply that the diffusion inside a cell is enhanced by activity of proteins. Mikhailov and Kapral proposed a model which suggests the possible mechanism for such diffusion enhancement. In the model, the conformational change of proteins is considered to induce fluctuating flow, that enhances diffusion. Moreover, when proteins are distributed non-uniformly, they induce not only diffusion enhancement but also the drift velocity of tracer particles. When there is a cluster of proteins with conformational change, the tracer particles tend to be accumulated into the cluster.
We have performed the high-pressure high-field ESR measurements on the orthogonal dimer spin system SrCu2(BO3)2 in THz region. By observing its low-lying states directly, we succeeded in detecting the quantum phase transition from the dimer singlet state to the plaquette singlet state at P=1.85±0.05 GPa. We also succeeded in determining the pressure dependence of the intradimer and interdimer exchange interactions J and J′ precisely. The corresponding critical point was obtained to be J′/J=0.660±0.003.
The quantum Hall effect (QHE) is one of the most remarkable phenomena in contemporary condensed matter physics, which rivals superconductivity in its fundamental significance as a manifestation of quantum mechanics on a macroscopic scale. The QHE has a topological property of quantum matter. There are two classes of QHE, where integer and fractional electrical conductance values are measured in units of e2/h. Here we report a novel type of quantization of thermal Hall effect caused by charge neutral quasiparticles, i.e. Majorana fermions, in an insulating two-dimensional (2D) quantum magnet, α-RuCl3 with honeycomb lattice. This material has been suggested to be a candidate of Kitaev quantum spin liquid (QSL), where significant entanglement of quantum spins is expected. In the low-temperature regime of the QSL state, the 2D thermal Hall conductance reaches a quantum plateau as a function of applied magnetic field. Surprisingly, the plateau attains a quantization value κxy2D/T=1/ 2(π 2/3)(k 2B /h), which is exactly half of that in the integer QHE. This half-integer thermal Hall conductance observed in a bulk material is a direct signature of topologically protected chiral edge currents of emergent Majorana fermions, whose degrees of freedom are half of those of electrons, and non-Abelian anyons in the bulk.
Permittivity is one of the most important parameters in condensed matter physics. It has been required not only experimentally to estimate materials and design optical devices, but also theoretically to discuss electronic structures and optical transitions. However, since control of polarization is diﬃcult in the soft X-ray energy region where there are many absorption edges, measuring permittivity has been impossible. We have succeeded in directly determining the complex permittivity tensor using a method combining a developed light source with polarization modulation and the magneto-optical Kerr effect in this energy region. The empirical permittivity has element speciﬁcity and perfect conﬁrmation using the ﬁrst-principles calculation for itinerant electrons systems. Here we show the detail and usefulness of the magneto-optical method using the new light source with permittivity spectra.