Deep variational quantum eigensolver for excited states and its application to quantum chemistry calculation of periodic materials

A programmable quantum device that has a large number of qubits without fault-tolerance has emerged recently. Variational quantum eigensolver (VQE) is one of the most promising ways to utilize the computational power of such devices to solve problems in condensed matter physics and quantum chemistry. As the size of the current quantum devices is still not large for rivaling classical computers at solving practical problems, Fujii et al. proposed a method called “Deep VQE”, which can provide the ground state of a given quantum system with the smaller number of qubits by combining the VQE and the technique of coarse graining [K. Fujii, K. Mitarai, W. Mizukami, and Y. O. Nakagawa, arXiv:2007.10917]. In this paper, we extend the original proposal of Deep VQE to obtain the excited states and apply it to quantum chemistry calculation of a periodic material, which is one of the most impactful applications of the VQE. We first propose a modified scheme to construct quantum states for coarse graining in Deep VQE to obtain the excited states. We also present a method to avoid a problem of meaningless eigenvalues in the original Deep VQE without restricting variational quantum states. Finally, we classically simulate our modified Deep VQE for quantum chemistry calculation of a periodic hydrogen chain as a typical periodic material. Our method reproduces the ground-state energy and the first-excited-state energy with the errors up to O(1)% despite the decrease in the number of qubits required for the calculation by two or four compared with the naive VQE. Our result will serve as a beacon for tackling quantum chemistry problems with classically-intractable sizes by smaller quantum devices in the near future

Fortnightly Variation of the Tsushima Warm Current on the Continental Shelf in the Southwestern Japan Sea

The first and second branches of the Tsushima Warm Current flow on the continental shelf and along the shelf break/slope in the southwestern Japan Sea, respectively. The second branch corresponds to the offshore side of the bottom temperature front between the offshore cold and nearshore warm waters. Across the Tsushima Warm Current on the continental shelf and the shelf edge, five bottom-mounted ADCPs with temperature sensors were deployed between middle June and late July 2014. At the shelf edge, the bottom temperature varied with the diurnal tidal cycle. The offshore bottom cold-water intruded into the continental shelf region in conjunction with the fortnightly spring-neap (2-week) cycle which is the modulation of the diurnal K1 and O1 internal tides. The bottom temperature front and the first branch of the Tsushima Warm Current on the continental shelf intensified in response to the bottom cold-water intrusion

Solving the degeneracy of the lepton-flavor mixing angle theta_atm by the T2KK two detector neutrino oscillation experiment

If the atmospheric neutrino oscillation amplitude, sin^2 2theta_atm is not maximal, there is a two fold ambiguity in the neutrino parameter space: sin^2 theta_atm>0.5 or sin^2 theta_atm<0.5. In this article, we study the impact of this degeneracy, the so-called octant degeneracy, on the T2KK experiment, which is a proposed extension of the T2K (Tokai-to-Kaimoka) neutrino oscillation experiment with an additional water cherenkov detector placed in Korea. We find that the degeneracy between sin^2 theta_atm= 0.40 and 0.60 can be resolved at the 3sigma level for sin^2 2theta_rct>0.12 (0.08) for the optimal combination of a 3.0^circ off-axis beam (OAB) at SK (L=295km) and a 0.5^circ OAB at L=1000km with a far detector of 100kton volume, after 5 years of exposure with 1.0(5.0) time 10^21 POT/year, if the hierarchy is normal. We also study the influence of the octant degeneracy on the capability of T2KK experiment to determine the mass hierarchy and the leptonic CP phase. The capability of rejecting the wrong mass hierarchy grows with increasing sin^2 theta_atm when the hierarchy is normal, whereas it is rather insensitive to sin^2 theta_atm for the inverted hierarchy. We also find that the 1sigma allowed region of the CP phase is not affected significantly even when the octant degeneracy is not resolved. All our results are obtained for the 22.5 kton Super-Kamiokande as a near detector and without an anti-neutrino beam.Comment: 23 pages, 9 figure

Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers

Efficacy of shear wave elasticity for evaluating myocardial hypertrophy in hypertensive rats

Shear wave (SW) imaging is a novel ultrasound-based technique for assessing tissue characteristics. SW elasticity may be useful to assess the severity of hypertensive left ventricular (LV) hypertrophy. This study aimed to evaluate the efficacy of SW elasticity for assessing the degree of myocardial hypertrophy using hypertensive rats. Rats were divided into hypertension group and control group. SW elasticity was measured on the excised heart. Myocardial hypertrophy was assessed histologically. LV weight was greater in hypertension group. An increase in interventricular septum and LV free wall thicknesses was observed in hypertension group. SW elasticity was significantly higher in hypertension group than in control group (14.6 +/- 4.3 kPa vs. 6.5 +/- 1.1 kPa, P < 0.01). The cross-sectional area of cardiomyocytes was larger in hypertension group than in control group (397 +/- 50 mu m(2) vs. 243 +/- 14 mu m(2), P < 0.01), and SW elasticity was positively correlated with the cross-sectional area of cardiomyocytes (R = 0.96, P < 0.01). This study showed that SW elasticity was higher in hypertensive rats and was closely correlated with the degree of myocardial hypertrophy, suggesting the efficacy of SW elasticity for estimating the severity of hypertensive LV hypertrophy

Impact of shear wave dispersion slope analysis for assessing the severity of myocarditis

This study aimed to elucidate the utility of a novel ultrasound-based technique, shear wave dispersion slope (SWDS) analysis, which estimates tissue viscosity, for evaluating the severity of myocardial inflammation. Experimental autoimmune myocarditis (EAM) at different disease phases [3-week (acute phase): n = 10, 5-week (subacute phase): n = 9, and 7-week (late phase): n = 11] were developed in male Lewis rats. SWDS was measured in the right and the left ventricular free walls (RVFW and LVFW) under a retrograde perfusion condition. Histological myocardial inflammation was evaluated by CD68 staining. The accumulation of CD68-positive cells was severe in the myocardium of the EAM 3-week group. The median (interquartile range) SWDS of RVFW was significantly higher in the EAM 3-week group [9.9 (6.5-11.0) m/s/kHz] than in the control group [5.4 (4.5-6.8) m/s/kHz] (P = 0.034). The median SWDS of LVFW was also significantly higher in the EAM 3-week group [8.1 (6.4-11.0) m/s/kHz] than in the control group [4.4 (4.2-4.8) m/s/kHz] (P = 0.003). SWDS and the percentage of CD68-positive area showed a significant correlation in RVFW (R-2 = 0.64, P < 0.001) and LVFW (R-2 = 0.73, P < 0.001). This study showed that SWDS was elevated in ventricular walls with acute inflammation and also significantly correlated with the degree of myocardial inflammation. These results suggest the potential of SWDS in estimating the histological severity of acute myocarditis

Deep internal tides near steep topographies southeast of Kyushu, Japan observed by the lowered acoustic Doppler current profiler (LADCP)

Abstract AOGS/AGU (WPGM) Joint Assembly at Singapore, 13-17 August, 201

A comprehensive survey on quantum computer usage: How many qubits are employed for what purposes?

Quantum computers (QCs), which work based on the law of quantum mechanics, are expected to be faster than classical computers in several computational tasks such as prime factoring and simulation of quantum many-body systems. In the last decade, research and development of QCs have rapidly advanced. Now hundreds of physical qubits are at our disposal, and one can find several remarkable experiments actually outperforming the classical computer in a specific computational task. On the other hand, it is unclear what the typical usages of the QCs are. Here we conduct an extensive survey on the papers that are posted in the quant-ph section in arXiv and claim to have used QCs in their abstracts. To understand the current situation of the research and development of the QCs, we evaluated the descriptive statistics about the papers, including the number of qubits employed, QPU vendors, application domains and so on. Our survey shows that the annual number of publications is increasing, and the typical number of qubits employed is about six to ten, growing along with the increase in the quantum volume (QV). Most of the preprints are devoted to applications such as quantum machine learning, condensed matter physics, and quantum chemistry, while quantum error correction and quantum noise mitigation use more qubits than the other topics. These imply that the increase in QV is fundamentally relevant, and more experiments for quantum error correction, and noise mitigation using shallow circuits with more qubits will take place.Comment: 14 pages, 5 figures, figures regenerate