Protecting dissipative quantum state preparation via dynamical decoupling

We show that dissipative quantum state preparation processes can be protected against qubit dephasing by interlacing the state preparation control with dynamical decoupling (DD) control consisting of a sequence of short $\pi$-pulses. The inhomogeneous broadening can be suppressed to second order of the pulse interval, and the protection efficiency is nearly independent of the pulse sequence but determined by the average interval between pulses. The DD protection is numerically tested and found to be efficient against inhomogeneous dephasing on two exemplary dissipative state preparation schemes that use collective pumping to realize many-body singlets and linear cluster states respectively. Numerical simulation also shows that the state preparation can be efficiently protected by $\pi$-pulses with completely random arrival time. Our results make possible the application of these state preparation schemes in inhomogeneously broadened systems. DD protection of state preparation against dynamical noises is also discussed using the example of Gaussian noise with a semiclasscial description.Comment: 9 pages, 8 figure

Effect of load introduction on graphite epoxy compression specimens

Compression testing of modern composite materials is affected by the manner in which the compressive load is introduced. Two such effects are investigated: (1) the constrained edge effect which prevents transverse expansion and is common to all compression testing in which the specimen is gripped in the fixture; and (2) nonuniform gripping which induces bending into the specimen. An analytical model capable of quantifying these foregoing effects was developed which is based upon the principle of minimum complementary energy. For pure compression, the stresses are approximated by Fourier series. For pure bending, the stresses are approximated by Legendre polynomials

Market versus administrative reallocation of agricultural land in a period of rapid industrialization

Under communal farm production, there was little incentive to work hard: the communal system guaranteed a livelihood, and there were few private gains from additional efforts. The reform that introduced the household responsibility system in China in the early 1980s sharpened individual work incentives by assigning specific plots and the rights to residual income to individual households. However, the household responsibility system left unresolved questions about the reallocation of land over time - questions that have become increasingly important (for both efficiency and equity) with the rapid growth of the non-farm economy. The authors use household and village data to show that the initially egalitarian distribution of land is becoming more dispersed over time. In what has become a hybrid property rights system, in some areas local village leaders (the cadre) were empowered to periodically redistribute land between households on the basis of economic and demographic changes among households. In other villages, households were granted much greater immunity against redistribution of any sort. Similarly, villages differed in the degree to which individual households could trade land among themselves. Some villages did not regulate the practice, and other required village approval or prohibited land rental relationships. The authors use simulated maximum likelihood methods to estimate hybrid panel models of the determinants of both market-based and administrative reallocation of land. They also use them to estimate the insecurity-induced investment costs of market-based reallocation of land. They find that administrative reallocation responds to the increasing inequality but non-market reallocations come at a significant cost in forgone investment.Labor Policies,Environmental Economics&Policies,Banks&Banking Reform,Public Sector Economics&Finance,Municipal Housing and Land,Environmental Economics&Policies,Banks&Banking Reform,Municipal Housing and Land,Urban Housing,Public Sector Economics&Finance

Viscous Effect on Surface Waves Generated by Steady Disturbances

A linearized theory is applied here to investigate the viscous effect on water waves generated and maintained by a system of external disturbances which is distributed over the free surface of an otherwise uniform flow. The flow is taken to be in the steady state configuration. The analysis is carried out to yield the asymptotic expressions for the surface wave when the Reynolds number of the flow is either large or small

Specialization without regret - transfer rights, agricultural productivity, and investment in an industrializing economy

A number of studies have examined the effects of secure tenure on agricultural investment and productivity. The authors also study the importance of rights to household residual income and land use being transferable. Contemporary China - where industrialization has spread rapidly, if unevenly - is a good place to study the economic effects of transfer rights as well as conventional security of tenure. Village collectives formally own land in China, so there can be no individual land sales, but farmers are sometimes entitled to sell their rights to use the land allocated to them under the household responsibility system. Whether a household has secure tenure depends on whether its landholding will be reduced if the household population declines, whether the landholding will be increased if the household population increases, and how frequent average land adjustments are under the household responsibility system. Analyzing panel data for a sample of farm households, the authors study the"investment regret mitigation effect", which results when greater transfer rights make households more willing to invest because they are less likely to regret such investments when they can recoup the investment value even if they exit farming. The authors find that transfer rights may be especially important in an industrializing economy. A property rights system with incomplete security of tenure but with strong transfer rights that permit"specialization without regret"- so farmers can recoup the value of an investment even if they exit farming - may have much to recommend it.Economic Theory&Research,Environmental Economics&Policies,Labor Policies,Banks&Banking Reform,Municipal Financial Management,Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Municipal Financial Management,Municipal Housing and Land

Space Alignment Based on Regularized Inversion Precoding in Cognitive Transmission

For a two-tier Multiple-Input Multiple-Output (MIMO) cognitive network with common receiver, the precoding matrix has a compact relationship with the capacity performance in the unlicensed secondary system. To increase the capacity of secondary system, an improved precoder based on the idea of regularized inversion for secondary transmitter is proposed. An iterative space alignment algorithm is also presented to ensure the Quality of Service (QoS) for primary system. The simulations reveal that, on the premise of achieving QoS for primary system, our proposed algorithm can get larger capacity in secondary system at low Signal-to-Noise Ratio (SNR), which proves the effectiveness of the algorithm