Measurement-free topological protection using dissipative feedback

Protecting quantum information from decoherence due to environmental noise is vital for fault-tolerant quantum computation. To this end, standard quantum error correction employs parallel projective measurements of individual particles, which makes the system extremely complicated. Here we propose measurement-free topological protection in two dimension without any selective addressing of individual particles. We make use of engineered dissipative dynamics and feedback operations to reduce the entropy generated by decoherence in such a way that quantum information is topologically protected. We calculate an error threshold, below which quantum information is protected, without assuming selective addressing, projective measurements, nor instantaneous classical processing. All physical operations are local and translationally invariant, and no parallel projective measurement is required, which implies high scalability. Furthermore, since the engineered dissipative dynamics we utilized has been well studied in quantum simulation, the proposed scheme can be a promising route progressing from quantum simulation to fault-tolerant quantum information processing.Comment: 17pages, 6 figure

Observations of SiO Maser Sources within a Few Parsec from the Galactic Center

Mapping and monitoring observations of SiO maser sources near the Galactic center were made with the Nobeyama 45-m telescope at 43 GHz. Rectangular mapping an area of approximately 200'' x 100''$ in a 30'' grid, and triangular mapping in a 20'' grid toward the Galactic center, resulted in 15 detections of SiO sources; the positions of the sources were obtained with errors of 5--10'', except for a few weak sources. Three-year monitoring observations found that the component at V_lsr=-27 km/s of IRS 10 EE flared to about 1.5 Jy during 2000 March--May, which was a factor of more than 5 brighter than its normal intensity. Using the radial velocities and positions of the SiO sources, we identified 5 which are counterparts of previously observed OH 1612 MHz sources. The other 10 SiO sources have no OH counterparts, but two were previously detected with VLA, and four are located close to the positions of large-amplitude variables observed at near-infrared wavelengths. A least-squares fit to a plot of velocities versus Galactic longitudes gives a rather high speed for the rotation of the star cluster around the Galactic center. The observed radial-velocity dispersion is roughly consistent with a value obtained before. It was found that all of the SiO sources with OH 1612 MHz counterparts have periods of light variation longer than 450 days, while SiO sources without OH masers often have periods shorter than 450 days. This fact suggests that lower-mass AGB stars are more often detected in SiO masers than in the OH 1612 MHz line.Comment: 9 pages, 7 figures. PASJ 54, No. 1 (2002) in pres

Forecasting skewness in stock returns: Evidence from firm-level data in Tokyo markets

Although it is well known that the market rate of return tends to show negative skewness, we find that the return distribution of individual stocks has shown positive skewness in the two principal Tokyo markets from 1980 to 2001. This is consistent with the results reported for the US market. Positive skewness in the returns is more evident for smaller firms. From our analysis of pooled cross-section data of individual stocks from 1990 to 2001, we find that there is clear evidence of the predictive power in the information up until the current period for the skewness in the following period. Specifically, a higher volatility and skewness in the return distribution of the current period is followed by a higher value of skewness in the following period. Also, the up trends in own returns in the preceding periods may explain the rather negatively skewed return distribution in the following period. Hong and Stein's (2003) model predicts a relation between turnover and skewness. For 1990 to 2001, negative relation to the skewness has been found to hold for smaller cap firms with past de-trended turnover. Furthermore, after the regulatory change in short-selling enacted in February 2002, we find more supportive evidence that high trend-adjusted turnover predicts more negative skewness in returns. Overall, our empirical evidence suggests that conditional skewness is partly explained by previous de-trended trading proxies, however, the results are not conclusive for the data in Tokyo markets

Boosting computational power through spatial multiplexing in quantum reservoir computing

Quantum reservoir computing provides a framework for exploiting the natural dynamics of quantum systems as a computational resource. It can implement real-time signal processing and solve temporal machine learning problems in general, which requires memory and nonlinear mapping of the recent input stream using the quantum dynamics in computational supremacy region, where the classical simulation of the system is intractable. A nuclear magnetic resonance spin-ensemble system is one of the realistic candidates for such physical implementations, which is currently available in laboratories. In this paper, considering these realistic experimental constraints for implementing the framework, we introduce a scheme, which we call a spatial multiplexing technique, to effectively boost the computational power of the platform. This technique exploits disjoint dynamics, which originate from multiple different quantum systems driven by common input streams in parallel. Accordingly, unlike designing a single large quantum system to increase the number of qubits for computational nodes, it is possible to prepare a huge number of qubits from multiple but small quantum systems, which are operationally easy to handle in laboratory experiments. We numerically demonstrate the effectiveness of the technique using several benchmark tasks and quantitatively investigate its specifications, range of validity, and limitations in detail.Comment: 15 page

Molecular Mechanisms Behind the Chemopreventive Effects of Anthocyanidins

Anthocyanins are polyphenolic ring-based flavonoids, and are widespread in fruits and vegetables of red-blue color. Epidemiological investigations and animal experiments have indicated that anthocyanins may contribute to cancer chemoprevention. The studies on the mechanism have been done recently at molecular level. This review summarizes current molecular bases for anthocyanidins on several key steps involved in cancer chemoprevention: (i) inhibition of anthocyanidins in cell transformation through targeting mitogen-activated protein kinase (MAPK) pathway and activator protein 1 (AP-1) factor; (ii) suppression of anthocyanidins in inflammation and carcinogenesis through targeting nuclear factor kappa B (NF-κB) pathway and cyclooxygenase 2 (COX-2) gene; (iii) apoptotic induction of cancer cells by anthocyanidins through reactive oxygen species (ROS) / c-Jun NH(2)-terminal kinase (JNK)-mediated caspase activation. These data provide a first molecular view of anthocyanidins contributing to cancer chemoprevention

温泉療法による気管支喘息に対する年間薬剤費の削減

Costs of drugs used for the treatment for 1 year were compared before and after spa therapy in 16 patients with asthma in relation to disease severity. Asthma severity was classified as : stage 1 (intermittent), 2 (mild persistent), 3(moderate persistent), and 4(severe persistent). 1. The total cost of drugs used for each pa-tient for 1 year clearty decreased in all groups. The % decrease of the costs of drugs in each group was 27.2% in patients with stage 1, 43.5% in those with stage 2 and 34.1% in those with stage 3-4 (mean 34.5% ). The reduction of the cost of bronchodilators was predominant in patients with stage 3-4, and the decrease in the cost of corticosteroids predominant in those with stage 2. The reduction of costs of antiallertgics, mucolytics, and antibiotics was predominant in patients with stage 2 and stage 3-4. The % reduction in the cost of corticostroids was remarkable in patients with stage 2. The % decrease in the costs of mucolytics and antibiotics was predomi-nant in patients with stage 2 and stage 3-4. The results obtained here suggest that the costs of drugs used for asthmatics could be reduced by long-term spa therapy, and the reduction of the costs was larger as asthma stage became more severe.気管支喘息16例を対象に,治療のために要した年間薬剤費が温泉療法により削減可能であるのかどうかについて,国際ガイドラインの重症度分類(stageト4)別に若干の検討を加えた｡1.年間の総薬剤費は重症度別の全てのグループにおいて明らかに減少した.2.その削減率は,ステージ1で27.2%,ステージ2で43.5%,ステージ3-4で34.1%であり,その平均は34.5%であった｡3.気管支拡張剤の薬剤費の減少はステージ3-4で高度であり,副腎皮質ホルモンの薬剤費の減少はステージ2で著明であった｡また,抗アレルギー薬,去痩薬,抗生物質などの薬剤費の削減は,ステージ2および3-4で高度であった｡4.削減率では,去壊薬,抗生物質の削減率が,2および3-4で著明であった｡ 以上の結果より,温泉療法により,気管支喘息の治療に必要な薬剤費は削減可能であること,そして,温泉療法による薬剤費の削減は職息の重症度が高い症例でより高度であることが示唆された