Quantum key distribution with an efficient countermeasure against correlated intensity fluctuations in optical pulses

Quantum key distribution (QKD) allows two distant parties to share secret keys with the proven security even in the presence of an eavesdropper with unbounded computational power. Recently, GHz-clock decoy QKD systems have been realized by employing ultrafast optical communication devices. However, security loopholes of high-speed systems have not been fully explored yet. Here we point out a security loophole at the transmitter of the GHz-clock QKD, which is a common problem in high-speed QKD systems using practical band-width limited devices. We experimentally observe the inter-pulse intensity correlation and modulation-pattern dependent intensity deviation in a practical high-speed QKD system. Such correlation violates the assumption of most security theories. We also provide its countermeasure which does not require significant changes of hardware and can generate keys secure over 100 km fiber transmission. Our countermeasure is simple, effective and applicable to wide range of high-speed QKD systems, and thus paves the way to realize ultrafast and security-certified commercial QKD systems

On the "KOMAKIBA" (cattles grazing on the afforestated land)

Keeping of Japanese Black Haired Cattle, especially for the benefit of getting calves, during the grass-grown season is of two method. One is intensive dry lot feeding and the other is extensive grazing. Recently, in Japan's Chiigoku mountainious district a grazing method, the grazing land is being afforestated remarkably. On the other hand, calves are being required for their more and faster growing. Now that, corresponding to the above-mentioned trend, KOMAKIBA (grazing on the afforestated land - a new foresd-grassland of the grazing system-) has come to appear. This paper is the first report on the its research. The results are summarized as follows: 1. The cattle are grazed mostly through 2 to 10 years on the afforestated land for a sow timber (red wood or cypress), privatly owned in general. 2. Grazing land is devided into a few blocks by fencing and cattle are grazing rotationally. 3. The cattle are grazing with individual farm severally. Heads of grazing per farm are 4~5, and the stocking rate is 1.2 or 1.0 head per hectare. 4. The degree of intensity of this system is intermediate between the intensive dry lot feeding and the extensive grazing. 5. There is no improvement yet in a grass growth. 6. Advantage (1) The vegetation-stand on the forest land with young growth is more productive than the treeless land. (2) Since the cattle willingly feed on weeds and leaves of bush under trees. Necessity for weeding and cutting out are decreased. (3) Excrements of the grazing cattle make more fertile soil and the soil gives more stimulus to a tree growth. (4) The possiblity of watch and management of the cattle in grazing is highly expected. 7. Disadvantage (1) There is some tramplings, but it is smoll. (2) Since there is no sufficient feed for calves' desire on the afforestated land. Some concentrate feed stuff is demanded additionary. In short, grazing system by KOMAKIBA makes promote a growth of cattle, saves a forestry works, and faciliates a tree growth. Conseqently, both the cattle and trees on the KOMAKIBA display the effects of supplementality with one another. 8. Some proved points that go deep into the researches. A. Technique (1) Behaviors of breeding herd on the KOMAKIBA. (2) Ecosystemic relationship of the tree crown and vegetation. (3) Improvement and management of the grass-growth on the afforestated land. (4) Increasing the efficiency for the management of grazing, and trimming-cut after the annual close of grazing. (5) Rational partition of the grazing block. (6) Afforestation planning taking into considerations the cattle grazing. B. Administration (1) Production economic relationship between trees and cattle on the afforestated land. (2) The disclimination of calves being raised for the breeding stock or the fattening. (3) More superior and more economical method in the production and storage for the roughage feed stuff. (4) Co-operation or division-labor in the cattle grazing. (5) Farm accounting and business analysis for the investments into KOMAKIBA. (6) The long-term schedule for the managerial combination of a forestry with a cattle grazing. (7) The rational selection and combination for the forest-grass-cultural lands on the cattle farming. C. Policy (1) To attach importance to KOMAKIBA system as the powerfull method for the regional development. (2) Reorganization or revision of existing system of owning and using in the forest and grass land considered for a cattle grazing. (3) To strengthen the national and individual policies for the development of KOMAKIBA system

A statistical modelling of the visual acuity measurement and its multiple test procedure

To establish the computer assisted system of the visual acuity test, we propose a statistical modelling of the visual acuity measurement and its multiple test procedure. The psychometric functions for individual patients are produced by the logistic regression combined with the guessing rate. We adopt test statistics based on (i) psychometric functions (the Cochran-Mantel-Haenszel method) and (ii) psychophysical thresholds (the delta method). The multiple comparisons are performed by the step-down procedure with Ryan-Einot-Gabriel-Welsch (REGW) significance levels. To show the practical effectiveness of our system, we present a numerical example of four patient groups

Coexistence of Continuous Variable Quantum Key Distribution and 7 ×\times 12.5 Gbit/s Classical Channels

We study coexistence of CV-QKD and 7 classical 12.5 Gbit/s on-off keying channels in WDM transmission over the C-band. We demonstrate key generation with a distilled secret key rate between 20 to 50 kbit/s in experiments running continuously over 24 hours.Comment: 2018 IEEE Summer Topicals, paper MD4.

Spreading of Antarctic Bottom Water examined using the CFC-11 distribution simulated by an eddy-resolving OGCM

We have investigated the spreading and pathway of Antarctic Bottom Water(AABW) using the simulated distribution of chlorofluorocarbons(CFCs) in a global eddy-resolving(1/10°) OGCM. Our goal is understanding of the processes and pathways determining the distribution of CFCs in the Southern Ocean, where much of this tracer is entrained by formation of deep and bottom water. The simu- lated high CFC-11 water reveals the newly formed AABW around the Antarctic Continent. The main source regions of AABW in the model are in the Weddell Sea(60°- 30°W ), offshore of Wilkes Land(120°- 160°E ) and in the Ross Sea(170°E -160°W ). In our model, spreading of simulated CFC-11 in the deep Southern Ocean from the newly formed AABW regions is more similar to the observed distribution than in coarse-resolution models. In the Weddell Sea, the high CFC-11 water spreads eastward with the Antarctic Circumpolar Current(ACC) and flows northward to the Argentine Basin. The high CFC-11 water from Wilkes Land joins with the high CFC-11 water from the Ross Sea. Some of the high CFC-11 water from Wilkes Land flows northward toward New Zealand. The high CFC-11 water from the Ross Sea flows eastward with the ACC along the Mid Ocean Ridge and northward to the Southeast Pacific Basin