No Infinite Tail Beats Optimal Spatial Search

Farhi and Gutmann (Physical Review A, 57(4):2403, 1998) proved that a continuous-time analogue of Grover search (also called spatial search) is optimal on the complete graphs. We extend this result by showing that spatial search remains optimal in a complete graph even in the presence of an infinitely long path (or tail). If we view the latter as an external quantum system that has a limited but nontrivial interaction with our finite quantum system, this suggests that spatial search is robust against a coherent infinite one-dimensional probe. Moreover, we show that the search algorithm is oblivious in that it does not need to know whether the tail is present or not, and if so, where it is attached to.Comment: 6 pages, 2 figures, 1 table. Fixed typo

Breaking the Speed Limit for Perfect Quantum State Transfer

We describe a protocol for perfectly transferring a quantum state from one party to another under the dynamics of a fixed, engineered Hamiltonian. Our protocol combines the concepts of fractional revival, dual rail encoding, and a rare glimpse of the anti-Zeno effect. Remarkably, the transfer happens faster than the speed limit for perfect quantum state transfer [1, 2].Comment: 5 pages, 1 figur

Of Shadows and Gaps in Spatial Search

Spatial search occurs in a connected graph if a continuous-time quantum walk on the adjacency matrix of the graph, suitably scaled, plus a rank-one perturbation induced by any vertex will unitarily map the principal eigenvector of the graph to the characteristic vector of the vertex. This phenomenon is a natural continuous-time analogue of Grover search. The spatial search is said to be optimal if it occurs with constant fidelity and in time inversely proportional to the shadow of the target vertex on the principal eigenvector. Extending a result of Chakraborty et al. (Physical Review A, 102:032214, 2020), we prove a simpler characterization of optimal spatial search. Based on this characterization, we observe that some families of distance-regular graphs, such as Hamming and Grassmann graphs, have optimal spatial search. We also show a matching lower bound on time for spatial search with constant fidelity, which extends a bound due to Farhi and Gutmann for perfect fidelity. Our elementary proofs employ standard tools, such as Weyl inequalities and Cauchy determinant formula.Comment: 23 pages, 3 figure

Quantum State Transfer in Graphs with Tails

We consider quantum state transfer on finite graphs which are attached to infinite paths. The finite graph represents an operational quantum system for performing useful quantum information tasks. In contrast, the infinite paths represent external infinite-dimensional systems which have limited (but nontrivial) interaction with the finite quantum system. We show that {\em perfect} state transfer can surprisingly still occur on the finite graph even in the presence of the infinite tails. Our techniques are based on a decoupling theorem for eventually-free Jacobi matrices, equitable partitions, and standard Lie theoretic arguments. Through these methods, we rehabilitate the notion of a dark subspace which had been so far viewed in an unflattering light.Comment: 25 pages, 7 figure

Molecular Docking of Potential Inhibitors for Influenza H7N9

As a new strain of virus emerged in 2013, avian influenza A (H7N9) virus is a threat to the public health, due to its high lethality and pathogenicity. Furthermore, H7N9 has already generated various mutations such as neuraminidase R294K mutation which could make the anti-influenza oseltamivir less effective or ineffective. In this regard, it is urgent to develop new effective anti-H7N9 drug. In this study, we used the general H7N9 neuraminidase and oseltamivir-resistant influenza virus neuraminidase as the acceptors and employed the small molecules including quercetin, chlorogenic acid, baicalein, and oleanolic acid as the donors to perform the molecular docking for exploring the binding abilities between these small molecules and neuraminidase. The results showed that quercetin, chlorogenic acid, oleanolic acid, and baicalein present oseltamivir-comparable high binding potentials with neuraminidase. Further analyses showed that R294K mutation in neuraminidase could remarkably decrease the binding energies for oseltamivir, while other small molecules showed stable binding abilities with mutated neuraminidase. Taken together, the molecular docking studies identified four potential inhibitors for neuraminidase of H7N9, which might be effective for the drug-resistant mutants

Discrete Element Simulation of the Shear Behavior of Binary Mixtures Composed of Spherical and Cubic Particles

This research paper presents an investigation into the shear behavior of binary mixtures composed of cubic and spherical particles, employing the discrete element method (DEM) through triaxial tests simulations. A range of binary particle samples with varying volume fractions of cubic and spherical particles is generated for analysis. The study primarily focuses on examining the contracting-dilatancy relationship of binary granular material samples by scrutinizing deviatoric stress and volumetric strain curves, while considering the influence of confining pressure, initial porosity, and particle size ratio. Furthermore, the paper sheds light on the evolution of microstructures during the shearing process by presenting coordination numbers and rotational velocity fields for different particle types (overall particles, cubic particles, spherical particles), as well as between cubic-spherical particles. The findings demonstrate the substantial impact of both the volume fraction of cubic particles and the particle size ratio on the shear behavior of binary particles at both macroscopic and microscopic scales. Additionally, a comprehensive investigation reveals the dependence of anisotropy in normal contact forces, tangent contact forces, and contact orientations on the volume fraction of cubic particles

Experimental and Numerical Investigations of Hydraulics in Water Intake with Stop-Log Gate

A stop-log gate, installed in water intake of hydropower project, has become an effective facility in achieving selective withdrawal and temperature control for the sake of benefiting downstream ecosystems. Hence, it is of great importance to comprehensively explore the water intake hydraulics with the gate, not limited to some specific case studies. This study deals, through laboratory experiments and numerical simulations, with flow features of such a gate-functioned intake. The physical model test is used to validate the numerical simulation. Subsequently, a series of numerical cases considering different hydraulic and geometric conditions are performed to help look into the behaviors. Particular attention is paid to the flow regimes, head loss and flow velocity distributions. The results showcase the effect of the gate on the intake flow regime, and in terms of head loss and flow velocity distribution, the influences of the upstream water head, intake chamber width and withdrawal depth are revealed in detail. An empirical expression, with regard to the coefficient of head loss, is derived and validated by data from the available literature. Moreover, it is found that the maximum velocity at trash rack section is dependent exclusively on the relative withdrawal depth and always occurs at a certain height range above the gate. These results may provide a meaningful reference for the research of water intake with similar situations.Validerad;2020;Nivå 2;2020-06-26 (alebob)</p

Hardware/Software Adaptive Cryptographic Acceleration for Big Data Processing

Along with the explosive growth of network data, security is becoming increasingly important for web transactions. The SSL/TLS protocol has been widely adopted as one of the effective solutions for sensitive access. Although OpenSSL could provide a freely available implementation of the SSL/TLS protocol, the crypto functions, such as symmetric key ciphers, are extremely compute-intensive operations. These expensive computations through software implementations may not be able to compete with the increasing need for speed and secure connection. Although there are lots of excellent works with the objective of SSL/TLS hardware acceleration, they focus on the dedicated hardware design of accelerators. Hardly of them presented how to utilize them efficiently. Actually, for some application scenarios, the performance improvement may not be comparable with AES-NI, due to the induced invocation cost for hardware engines. Therefore, we proposed the research to take full advantages of both accelerators and CPUs for security HTTP accesses in big data. We not only proposed optimal strategies such as data aggregation to advance the contribution with hardware crypto engines, but also presented an Adaptive Crypto System based on Accelerators (ACSA) with software and hardware codesign. ACSA is able to adopt crypto mode adaptively and dynamically according to the request character and system load. Through the establishment of 40 Gbps networking on TAISHAN Web Server, we evaluated the system performance in real applications with a high workload. For the encryption algorithm 3DES, which is not supported in AES-NI, we could get about 12 times acceleration with accelerators. For typical encryption AES supported by instruction acceleration, we could get 52.39% bandwidth improvement compared with only hardware encryption and 20.07% improvement compared with AES-NI. Furthermore, the user could adjust the trade-off between CPU occupation and encryption performance through MM strategy, to free CPUs according to the working requirements