Holographic Storage of Biphoton Entanglement

Coherent and reversible storage of multi-photon entanglement with a multimode quantum memory is essential for scalable all-optical quantum information processing. Although single photon has been successfully stored in different quantum systems, storage of multi-photon entanglement remains challenging because of the critical requirement for coherent control of photonic entanglement source, multimode quantum memory, and quantum interface between them. Here we demonstrate a coherent and reversible storage of biphoton Bell-type entanglement with a holographic multimode atomic-ensemble-based quantum memory. The retrieved biphoton entanglement violates Bell's inequality for 1 microsecond storage time and a memory-process fidelity of 98% is demonstrated by quantum state tomography.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let

Universal critical properties of the Eulerian bond-cubic model

We investigate the Eulerian bond-cubic model on the square lattice by means of Monte Carlo simulations, using an efficient cluster algorithm and a finite-size scaling analysis. The critical points and four critical exponents of the model are determined for several values of $n$. Two of the exponents are fractal dimensions, which are obtained numerically for the first time. Our results are consistent with the Coulomb gas predictions for the critical O($n$) branch for $n < 2$ and the results obtained by previous transfer matrix calculations. For $n=2$, we find that the thermal exponent, the magnetic exponent and the fractal dimension of the largest critical Eulerian bond component are different from those of the critical O(2) loop model. These results confirm that the cubic anisotropy is marginal at $n=2$ but irrelevant for $n<2$

Screwing assembly oriented interactive model segmentation in HMD VR environment

© 2019 John Wiley & Sons, Ltd. Although different approaches of segmenting and assembling geometric models for 3D printing have been proposed, it is difficult to find any research studies, which investigate model segmentation and assembly in head-mounted display (HMD) virtual reality (VR) environments for 3D printing. In this work, we propose a novel and interactive segmentation method for screwing assembly in the environments to tackle this problem. Our approach divides a large model into semantic parts with a screwing interface for repeated tight assembly. Specifically, after a user places the cutting interface, our algorithm computes the bounding box of the current part automatically for subsequent multicomponent semantic Boolean segmentations. Afterwards, the bolt is positioned with an improved K3M image thinning algorithm and is used for merging paired components with union and subtraction Boolean operations respectively. Moreover, we introduce a swept Boolean-based rotation collision detection and location method to guarantee a collision-free screwing assembly. Experiments show that our approach provides a new interactive multicomponent semantic segmentation tool that supports not only repeated installation and disassembly but also tight and aligned assembly

A statistical investigation of the rheological properties of magnesium phosphate cement

Magnesium phosphate cement (MPC) is a promising material applied for rapid patch repairing in civil engineering and waste immobilisation in nuclear industry. However, the rheological properties of this new binder material which highly affects its engineering application, is to be explored. The current work aims at investigating the rheological properties of MPC along 98 with determining the optimum conditions to obtain MPC materials with desirable rheological performances. The Response Surface Methodology (RSM) accompanied by Central Composite Design (CCD) were adopted to establish mathematical model describing the rheological characteristics of MPC in terms of yield stress (Pa) and plastic viscosity (Pa.s), as a function of three independent variables namely W/S ratio, M/P ratio and Borax dosage. The analysis of variance (ANOVA) was also conducted to assess the significance and adequacy of the regression models attained. The results showed that the M/P ratio and Borax dosage could affect significantly the yield stress of MPC, while W/S ratio was the significant coefficient influencing the plastic viscosity. The numerical optimised values of the W/S ratio, M/P ratio and Borax dosage were 0.25, 8.97 and 0.17 respectively, and a MPC paste with desirable rheological characteristics (yield stress of 0.40 Pa and plastic viscosity of 0.93 Pa.s) can be obtained. Further experiments will be carried out to verify the predicted optimum conditions and study the interactions between the factors in relation to the responses

Efficient and Realistic Character Animation through Analytical Physics-based Skin Deformation

Physics-based skin deformation methods can greatly improve the realism of character animation, but require non-trivial training, intensive manual intervention, and heavy numerical calculations. Due to these limitations, it is generally time-consuming to implement them, and difficult to achieve a high runtime efficiency. In order to tackle the above limitations caused by numerical calculations of physics-based skin deformation, we propose a simple and efficient analytical approach for physicsbased skin deformations. Specifically, we (1) employ Fourier series to convert 3D mesh models into continuous parametric representations through a conversion algorithm, which largely reduces data size and computing time but still keeps high realism, (2) introduce a partial differential equation (PDE)-based skin deformation model and successfully obtain the first analytical solution to physics-based skin deformations which overcomes the limitations of numerical calculations. Our approach is easy to use, highly efficient, and capable to create physically realistic skin deformations

Immobilisation of caesium in magnesium phosphate-based blends

Disposal of Caesium (Cs) by incorporating it into host matrices has been proved as a promising concept. Even though Portland cement (PC) based systems can be used to encapsulate low (LLW) or intermediate level waste (ILW), they are not efficient for immobilising Cs due to the very high water-solubility of Cs. Magnesium phosphate cement (MPC), a chemically bonded ceramic consists of struvite families produced by the acid based reactions between dead-burnt magnesium oxide (MgO) and phosphates (e.g., KH2PO4), can be a potential candidate for hosting Cs, since it has been reported that Cs can be incorporated in the Kstruvite structures by substituting potassium (K) to form (K,Cs)-struvite. However, the acid-based reaction to form MPC under ambient temperature between magnesium oxide (MgO) and phosphates (e.g., KH2PO4) is violent and exothermic, which raises concerns about industrial application of MPC in real world. In this work, ground-granulated blast-furnace slag (GGBS) and pulverised fuel ash were used to replace MPC in order to reduce the heat released. The feasibility of MPC, as well as MPC-based blends, i.e. GGBS-MPC or PFAMPC matrices, for immobilising Cs was assessed by their leaching behaviour at the ages of 3d, 7d and 28d. In addition, two typical PC based systems currently used in nuclear waste immobilisation, i.e., pure PC and PC-GGBS (1:9) mixes, were also produced and tested as controls. The results indicated that all the MPC mixes, including pure MPC, GGBS-MPC and PFA-MPC, demonstrated superb capability for immobilising Cs, with the immobilisation rates achieved more than 99.5% at all curing age investigated. Compared to the traditional PC and PC/GGBS mixes, the MPC mixes nearly doubled the Cs immobilisation rate, which is rather encouraging

Storage of 1650 modes of single photons at telecom wavelength

To advance the full potential of quantum networks one should be able to distribute quantum resources over long distances at appreciable rates. As a consequence, all components in the networks need to have large multimode capacity to manipulate photonic quantum states. Towards this end, a multimode photonic quantum memory, especially one operating at telecom wavelength, remains a key challenge. Here we demonstrate a spectro-temporally multiplexed quantum memory at 1532 nm. Multimode quantum storage of telecom-band heralded single photons is realized by employing the atomic frequency comb protocol in a 10-m-long cryogenically cooled erbium doped silica fibre. The multiplexing encompasses five spectral channels - each 10 GHz wide - and in each of these up to 330 temporal modes, resulting in the simultaneous storage of 1650 modes of single photons. Our demonstrations open doors for high-rate quantum networks, which are essential for future quantum internet

Scattering of short laser pulses from trapped fermions

We investigate the scattering of intense short laser pulses off trapped cold fermionic atoms. We discuss the sensitivity of the scattered light to the quantum statistics of the atoms. The temperature dependence of the scattered light spectrum is calculated. Comparisons are made with a system of classical atoms who obey Maxwell-Boltzmann statistics. We find the total scattering increases as the fermions become cooler but eventually tails off at very low temperatures (far below the Fermi temperature). At these low temperatures the fermionic degeneracy plays an important role in the scattering as it inhibits spontaneous emission into occupied energy levels below the Fermi surface. We demonstrate temperature dependent qualitative changes in the differential and total spectrum can be utilized to probe quantum degeneracy of trapped Fermi gas when the total number of atoms are sufficiently large $(\geq 10^6)$. At smaller number of atoms, incoherent scattering dominates and it displays weak temperature dependence.Comment: updated figures and revised content, submitted to Phys.Rev.