Optimal measurements to access classical correlations of two-qubit states

We analyze the optimal measurements accessing classical correlations in arbitrary two-qubit states. Two-qubit states can be transformed into the canonical forms via local unitary operations. For the canonical forms, we investigate the probability distribution of the optimal measurements. The probability distribution of the optimal measurement is found to be centralized in the vicinity of a specific von Neumann measurement, which we call the maximal-correlation-direction measurement (MCDM). We prove that for the states with zero-discord and maximally mixed marginals, the MCDM is the very optimal measurement. Furthermore, we give an upper bound of quantum discord based on the MCDM, and investigate its performance for approximating the quantum discord.Comment: 8 pages, 3 figures, version accepted by Phys. Rev.

Modeling Risk Behavior of Agricultural Production in Chinese Small Households

This paper analyzed Chinese small-scale farmer's response to agricultural risks by using MOTAD model. Based on the household's data from the two villages Wangjia and Damao in Zhejiang province, we established "representative rural household" for each of the sampling villages. The results show that farmers in Zhejiang are quite sensitive to agricultural risks. However, different farming systems, the ratio of agricultural income to total family income, as well as the size of arable land, differentiates their risk response. The decision maker's risk preference not only affects the type of agricultural activities and corresponding scales they selected, but also have further effects on the micro agricultural production structure and stable growth of household's income. Given the amount of productive resources such as arable land, capital and labor force, the combination of production activities with a higher level of expected income/risk would be selected if the decision maker is willing to take risks. In a higher level of risks, capital is invested prior to manpower, implying that the latter has a much higher opportunity cost. For those combinations with a lower risk level, diversification might reduce risks to some extent at a cost of total return. Current agriculture structure needs to be adjusted and improved.Farming household, agricultural risks, risk response, MOTAD Model, Farm Management, Risk and Uncertainty, D1, C6, D2,

Transmission of doughnut light through a bull's eye structure

We experimentally investigate the extraordinary optical transmission of doughnut light through a bull's eye structure. Since the intensity is vanished in the center of the beam, almost all the energy reaches the circular corrugations (not on the hole), excite surface plasmons which propagate through the hole and reradiate photons. The transmitted energy is about 57 times of the input energy on the hole area. It is also interesting that the transmitted light has a similar spatial shape with the input light although the diameter of the hole is much smaller than the wavelength of light.Comment: 3 pages,4 figure