Entangling distant solid-state spins via thermal phonons

The implementation of quantum entangling gates between qubits is essential to achieve scalable quantum computation. Here, we propose a robust scheme to realize an entangling gate for distant solid-state spins via a mechanical oscillator in its thermal equilibrium state. By appropriate Hamiltonian engineering and usage of a protected subspace, we show that the proposed scheme is able to significantly reduce the thermal effect of the mechanical oscillator on the spins. In particular, we demonstrate that a high entangling gate fidelity can be achieved even for a relatively high thermal occupation. Our scheme can thus relax the requirement for ground-state cooling of the mechanical oscillator, and may find applications in scalable quantum information processing in hybrid solid-state architectures.Comment: 11 pages, 4 figure

Synthetic tensor gauge fields

Synthetic gauge fields have provided physicists with a unique tool to explore a wide range of fundamentally important phenomena in physics. However, only synthetic vector gauge fields are currently available in experiments. The study of tensor gauge fields, which play a vital role in fracton phase of matter, remains purely theoretical. Here, we propose schemes to realize synthetic tensor gauge fields using techniques readily available in laboratories. A lattice tilted by a strong linear potential and a weak quadratic potential naturally yields a rank-2 electric field for a lineon formed by a particle-hole pair. Such a rank-2 electric field leads to a new type of Bloch oscillations, where neither a single particle nor a single hole responds but a lineon vibrates. A synthetic vector gauge field carrying a position-dependent phase could also be implemented to produce the same synthetic tensor gauge field for a lineon. In higher dimensions, the interplay between interactions and vector gauge potentials imprints a phase to the ring-exchange interaction and thus generates synthetic tensor gauge fields for planons. Such tensor gauge fields make it possible to realize a dipolar Harper-Hofstadter model in laboratories.Comment: 6+3 pages, 4+3 figure

Heterogeneity of Soil Nutrients: A Review of Methodology, Variability and Impact Factors

Soil nutrient heterogeneity highly correlates to plant growth and development of environmental quality. In order to better understand nutrient cycling, heterogeneity of soil nutrients and their driving mechanism in different land use types were summarized from 1945 to 2016. By grouping keywords indexed in the titles of articles from the data base of Web of Science, two hundred and thirty one publications related to our topics were used for analysis. Soil sampling and statistical method were compared, and spatial dependence and the impact factors for soil organic matter (SOM), Nitrogen (N), Phosphorus (P) and Potassium (K). The results showed that soil nutrient heterogeneity was influenced by different factors at different scales. The spatial dependence of SOM, N and P were mainly at the moderate level (48.9-59.0%) and strong level (33.3-42.2%), while for K was at strong level (63.6-84.6%) and moderate level (15.4-36.4%). This was mainly influenced by topography, soil loss, weather condition, parent material, soil type, soil texture, land use, human activities, soil moisture, mineral element, soil structure, animal and plant. These impact factors were summarized separately, and the influence of factors at different spatiotemporal scales was discussed. At the end of the review, the ideas for further research were postulated

Evaluation of environmental purification service for Urban Green Space in Nanjing

Urban environmental pollution intensifies with the acceleration of industrialization and urbanization. Urban green space plays an important role in improving the quality of urban environment. Statistical reports from 2002 to 2013 were analysed to estimate the environmental purification value of urban green space in Nanjing by using the production cost method and substituted expenses method. Results showed that the environmental purification value of urban green space from 2002 to 2013 increased from 0.212 billion to 0.354 billion RMB, showing an increase of 0.142 billion RMB and an annual average growth rate of 14% in the past 12 years. Carbon fixation and oxygen release of urban green space ecosystems are transferable in regional space; hence, these services can be performed by the natural ecosystems beyond the city. However, harmful gas absorption, dust detention and noise reduction of urban green space is not transferable in space and thus must be performed by the urban ecosystem. Therefore, aside from innovating technologies for pollution-reducing and pollution-controlling, increasing green space coverage, optimizing green plant distribution structure, and enhancing urban green space management must be executed to improve the urban ecological environment

Heterogeneity of Soil Nutrients: A Review of Methodology, Variability and Impact Factors

Soil nutrient heterogeneity highly correlates to plant growth and development of environmental quality. In order to better understand nutrient cycling, heterogeneity of soil nutrients and their driving mechanism in different land use types were summarized from 1945 to 2016. By grouping keywords indexed in the titles of articles from the data base of Web of Science, two hundred and thirty one publications related to our topics were used for analysis. Soil sampling and statistical method were compared, and spatial dependence and the impact factors for soil organic matter (SOM), Nitrogen (N), Phosphorus (P) and Potassium (K). The results showed that soil nutrient heterogeneity was influenced by different factors at different scales. The spatial dependence of SOM, N and P were mainly at the moderate level (48.9-59.0%) and strong level (33.3-42.2%), while for K was at strong level (63.6-84.6%) and moderate level (15.4-36.4%). This was mainly influenced by topography, soil loss, weather condition, parent material, soil type, soil texture, land use, human activities, soil moisture, mineral element, soil structure, animal and plant. These impact factors were summarized separately, and the influence of factors at different spatiotemporal scales was discussed. At the end of the review, the ideas for further research were postulated

Reweighting Clicks with Dwell Time in Recommendation

The click behavior is the most widely-used user positive feedback in recommendation. However, simply considering each click equally in training may suffer from clickbaits and title-content mismatching, and thus fail to precisely capture users' real satisfaction on items. Dwell time could be viewed as a high-quality quantitative indicator of user preferences on each click, while existing recommendation models do not fully explore the modeling of dwell time. In this work, we focus on reweighting clicks with dwell time in recommendation. Precisely, we first define a new behavior named valid read, which helps to select high-quality click instances for different users and items via dwell time. Next, we propose a normalized dwell time function to reweight click signals in training, which could better guide our model to provide a high-quality and efficient reading. The Click reweighting model achieves significant improvements on both offline and online evaluations in a real-world system.Comment: 5 pages, under revie

Engineering artificial atomic systems of giant electric dipole moment

The electric dipole moment (EDM) plays a crucial role in determining the interaction strength of an atom with electric fields, making it paramount to quantum technologies based on coherent atomic control. We propose a scheme for engineering the potential in a Paul trap to realize a two-level quantum system with a giant EDM formed by the motional states of a trapped electron. We show that, under realistic experimental conditions, the EDM can significantly exceed the ones attainable with Rydberg atoms. Furthermore, we show that such artificial atomic dipoles can be efficiently initialized, readout, and coherently controlled, thereby providing a potential platform for quantum technologies such as ultrahigh-sensitivity electric-field sensing.Comment: 7 pages, 4 5 figures + 26 pages Supplemental Material. Comments are welcom

Kinetic study of the reaction of OH with CH2I2

Flash photolysis (FP) coupled to resonance fluorescence (RF) was used to measure the absolute rate coefficients (k1) for the reaction of OH(X2P) radicals with diiodomethane (CH2I2) over the temperature range 295374 K. The experiments involved time-resolved RF detection of the OH (A2∑+→X2Π transition at λ = 308 nm) following FP of the H2O/CH2I 2/He mixtures. The OH(X2Π) radicals were produced by FP of H2O in the vacuum-UV at wavelengths l 4 120 nm. Decays of OH radicals in the presence of CH2I2 are observed to be exponential, and the decay rates are found to be linearly dependent on the CH2I 2 concentration. The results are described by the Arrhenius expression k1(T) = (4.2 ± 0.5) × 1011 exp[-(670 ± 20)K/T] cm3 molecule-1 s-1. The implications of the reported kinetic results for understanding the atmospheric chemistry of CH2I2 are discussed. © 2011 the Owner Societies