Singularity Analysis for a 5-DoF FullySymmetrical Parallel Manipulator 5-RRR (RR

Abstract-A 5-DoF 3R2T (three dimensional rotation and two dimensional translation degrees of freedom) fully-symmetrical parallel manipulator can be adopted in many applications such as simulating the motion of spinal column. However, kinematics of this type parallel manipulator has not been studied enough because of short history. The study of kinematics of the manipulators leads inevitably to the problem of singular configuration. Singularity of a 5-DoF 3R2T fully-symmetrical parallel manipulator, 5-RRR(RR), is illustrated in this study. According to the singularity classification by Fang and Tsai, both limb singularity and actuation singularity are illustrated by screw theory and Grassmann geometry. The result of this study will be helpful for singularity analysis of 5-DoF 3R2T fully-symmetrical parallel manipulators because of their similar constraint property

Observation of quantum fingerprinting beating the classical limit

Quantum communication has historically been at the forefront of advancements, from fundamental tests of quantum physics to utilizing the quantum-mechanical properties of physical systems for practical applications. In the field of communication complexity, quantum communication allows the advantage of an exponential reduction in the information transmitted over classical communication to accomplish distributed computational tasks. However, to date, demonstrating this advantage in a practical setting continues to be a central challenge. Here, we report an experimental demonstration of a quantum fingerprinting protocol that for the first time surpasses the ultimate classical limit to transmitted information. Ultra-low noise superconducting single-photon detectors and a stable fibre-based Sagnac interferometer are used to implement a quantum fingerprinting system that is capable of transmitting less information than the classical proven lower bound over 20 km standard telecom fibre for input sizes of up to two Gbits. The results pave the way for experimentally exploring the advanced features of quantum communication and open a new window of opportunity for research in communication complexity and testing the foundations of physics.Comment: 19 pages, 4 figure

Bromidotricarbon­yl[2-(pyridin-2-yl-κN)-5-p-tolyl-1,3,4-oxadiazole-κN 3]rhenium(I) dichloro­methane monosolvate

In the title compound, [ReBr(C14H11N3O)(CO)3]·CH2Cl2, the coordination geometry of the ReI atom is a distorted ReC3N2Br octa­hedron with the carbonyl C atoms in a fac arrangement. Within the 2-(pyridin-2-yl)-5-p-tolyl-1,3,4-oxadiazole ligand, the dihedral angles between the oxadiazole ring and the pyridine (py) and benzene (bz) rings are 1.7 (2) and 7.1 (2)°, respectively, and the dihedral angle between the py and bz rings is 5.5 (2)°. In the crystal, aromatic π–π stacking between the oxadiazole rings of adjacent mol­ecules [centroid–centroid separation = 3.465 (3) Å] is seen

2-(4-Methyl­phen­yl)-1-(phenyl­sulfon­yl)propan-2-ol

The title compound, C16H18O3S, features a U-shape mol­ecular structure with a dihedral angle between the terminal benzene rings of 20.8 (1)°. An intra­molecular O—H⋯O hydrogen bond helps to stabilize the mol­ecular structure. Inter­molecular classical O—H⋯O and weak C—H⋯O hydrogen bonding is present in the crystal structure

Bromidotricarbon­yl[2-phenyl-5-(pyridin-2-yl-κN)-1,3,4-oxadiazole-κN 4]rhenium(I) dichloro­methane monosolvate

In the title rhenium(I) complex, [ReBr(C13H9N3O)(CO)3]·CH2Cl2, the dichloro­methane solvent mol­ecule is disordered over two positions with an occupancy ratio of 0.81 (15):0.19 (15). The ReI atom is coordinated by two N atoms from a 2-phenyl-5-(pyridin-2-yl-κN)-1,3,4-oxadiazole (L) ligand, three C atoms from three carbonyl groups and a Br atom in a distorted octa­hedral geometry. The three rings in L are almost coplanar (a mean plane fitted through all non-H atoms of this ligand has an r.m.s. deviation of 0.063 Å), and the carbonyl ligands are coordinated in a fac arrangement

Measurement-device-independent quantum key distribution over untrustful metropolitan network

Quantum cryptography holds the promise to establish an information-theoretically secure global network. All field tests of metropolitan-scale quantum networks to date are based on trusted relays. The security critically relies on the accountability of the trusted relays, which will break down if the relay is dishonest or compromised. Here, we construct a measurement-device-independent quantum key distribution (MDIQKD) network in a star topology over a 200 square kilometers metropolitan area, which is secure against untrustful relays and against all detection attacks. In the field test, our system continuously runs through one week with a secure key rate ten times larger than previous result. Our results demonstrate that the MDIQKD network, combining the best of both worlds --- security and practicality, constitutes an appealing solution to secure metropolitan communications.Comment: 17 pages, 4 figure