Functional quantum nodes for entanglement distribution over scalable quantum networks

We demonstrated entanglement distribution between two remote quantum nodes located 3 meters apart. This distribution involves the asynchronous preparation of two pairs of atomic memories and the coherent mapping of stored atomic states into light fields in an effective state of near-maximum polarization entanglement. Entanglement is verified by way of the measured violation of a Bell inequality, and it can be used for communication protocols such as quantum cryptography. The demonstrated quantum nodes and channels can be used as segments of a quantum repeater, providing an essential tool for robust long-distance quantum communication.     

Correcting quantum errors with entanglement

We show how entanglement shared between encoder and decoder can simplify the theory of quantum error correction. The entanglement-assisted quantum codes we describe do not require the dual-containing constraint necessary for standard quantum error-correcting codes, thus allowing us to "quantize" all of classical linear coding theory. In particular, efficient modern classical codes that attain the Shannon capacity can be made into entanglement-assisted quantum codes attaining the hashing bound (closely related to the quantum capacity). For systems without large amounts of shared entanglement, these codes can also be used as catalytic codes, in which a small amount of initial entanglement enables quantum communication.     

Optically induced entanglement of excitons in a single quantum Dot

Optically induced entanglement is identified by the spectrum of the phase-sensitive homodyne-detected coherent nonlinear optical response in a single gallium arsenide quantum dot. The electron-hole entanglement involves two magneto-excitonic states differing in transition energy and polarization. The strong coupling needed for entanglement is provided through the Coulomb interaction involving the electrons and holes. The result presents a first step toward the optical realization of quantum logic operations using two or more quantum dots.     

Long-distance dispersal of plants

Long-distance dispersal (LDD) of plants poses challenges to research because it involves rare events driven by complex and highly stochastic processes. The current surge of renewed interest in LDD, motivated by growing recognition of its critical importance for natural populations and communities and for humanity, promises an improved, quantitatively derived understanding of LDD. To gain deep insights into the patterns, mechanisms, causes, and consequences of LDD, we must look beyond the standard dispersal vectors and the mean trend of the distribution of dispersal distances. "Nonstandard" mechanisms such as extreme climatic events and generalized LDD vectors seem to hold the greatest explanatory power for the drastic deviations from the mean trend, deviations that make the nearly impossible LDD a reality.     

Unconditional security of quantum key distribution over arbitrarily long distances

Quantum key distribution is widely thought to offer unconditional security in communication between two users. Unfortunately, a widely accepted proof of its security in the presence of source, device, and channel noises has been missing. This long-standing problem is solved here by showing that, given fault-tolerant quantum computers, quantum key distribution over an arbitrarily long distance of a realistic noisy channel can be made unconditionally secure. The proof is reduced from a noisy quantum scheme to a noiseless quantum scheme and then from a noiseless quantum scheme to a noiseless classical scheme, which can then be tackled by classical probability theory.     

Step-by-step engineered multiparticle entanglement

After quantum particles have interacted, they generally remain in an entangled state and are correlated at a distance by quantum-mechanical links that can be used to transmit and process information in nonclassical ways. This implies programmable sequences of operations to generate and analyze the entanglement of complex systems. We have demonstrated such a procedure for two atoms and a single-photon cavity mode, engineering and analyzing a three-particle entangled state by a succession of controlled steps that address the particles individually. This entangling procedure can, in principle, operate on larger numbers of particles, opening new perspectives for fundamental tests of quantum theory.     

Environment-induced sudden death of entanglement

We demonstrate the difference between local, single-particle dynamics and global dynamics of entangled quantum systems coupled to independent environments. Using an all-optical experimental setup, we showed that, even when the environment-induced decay of each system is asymptotic, quantum entanglement may suddenly disappear. This "sudden death" constitutes yet another distinct and counterintuitive trait of entanglement.     

长距离输气管道的优化设计

基于气体在管道中一元流动的连续性方程、状态方程、运动方程和能量方程,建立数学模型并确定边界条件,利用四阶龙格-库塔法进行数值求解,使用VB程序设计语言编写计算程序,在确保管道经济效益最佳的情况下,对管道主要参数进行优化设计。经算例验证,该设计方法可为管道优化设计提供一定参考。     

国产化长输管道输油泵的研制

通过对输油泵总体结构、水力设计方法、铸造加工工艺、高压机械密封、可靠性检测等方面的设计研究,解决了国产化输油泵效率低、可靠性差等问题,研制完成的管道输油泵经现场运行验证,取得了预期的使用效果,具有较好的推广应用价值.     

植物硼的长距离运输

综述了硼在植物中长距离运输特别是韧皮部运输的研究进展，大多数植物中，硼主要通过木质部运输，但不排除在蒸腾作用较弱的部位，特别是缺硼胁迫时，韧皮部对硼运输起一定作用，而对于以山梨醇，甘露醇，半乳糖醇等多元醇为光合作用初级运输物的植物中，硼可以与多元醇形成络合物而在韧皮部中自由运输。硼是目前已知的在不同植物韧皮部中移动性相差最大的营养元素，韧皮部中硼运输基因型差异机制的深入研究可为改良植物硼的运输和再利用特性提供理论依据。     

长输管道阴极保护故障分析

分析了长输管道阴极保护系统中出现的各种故障,并根据各种故障的特点,将阴极保护故障分类三类。恒电位仪故障和电缆,参比,阳极故障属于第一类;绝缘法兰故障和防腐覆盖层故障属于第二类,外部交、直流电干扰与其它金属体搭接和外部工程引起的故障属于第三类,分别对这三类故障提出了不同的解决方法。     

Heralded entanglement between widely separated atoms

Entanglement is the essential feature of quantum mechanics. Notably, observers of two or more entangled particles will find correlations in their measurement results that cannot be explained by classical statistics. To make it a useful resource, particularly for scalable long-distance quantum communication, the heralded generation of entanglement between distant massive quantum systems is necessary. We report on the creation and analysis of heralded entanglement between spins of two single rubidium-87 atoms trapped independently 20 meters apart. Our results illustrate the viability of an integral resource for quantum information science, as well as for fundamental tests of quantum mechanics.