Search

We evaluate analytically the quantum discord for a large family of multiqubit states. It is interesting to note that the quantum discord of three-qubits and five-qubits is the same, as is the quantum discord of two-qubits and six-qubits. We discover that the quantum discord of this family states can be concluded into three categories. The level surfaces of the quantum discord in the three categories is shown through images. Furthermore, we investigated the dynamic behavior of quantum discord under decoherence. For the odd partite systems, we prove the frozen phenomenon of quantum discord doesn't exist under the phase flip channel, while it can be found in the even partite systems., 9 pages, 2 figures, comments are welcome!. arXiv admin note: text overlap with arXiv:2104.12344

This paper investigates the vibrations and acoustic noise behavior of some equal tooth width, unequal tooth width and modular surface mounted permanent magnet machines. The investigations are based on finite element analysis (ANSYS) and the performances such as radial force (and airgap magnetic pressure), vibration modes (shapes and resonant frequencies), radial displacement and acceleration of the stator, and sound pressure level have been calculated and compared amongst different machines. It has been found that due to the existence of flux gaps in stator alternate teeth, at the same operating condition (phase current and rotor speed), the modular machines can reduce the sound pressure level by up to 15dB compared to the equal tooth width permanent magnet machines. A similar reduction in sound pressure level can be achieved by adopting the unequal tooth width permanent magnet machine.

We investigate the optimal convex approximation of the quantum state with respect to a set of available states. By isometric transformation, we have presented the general mathematical model and its solutions together with a triple uncertainty equality relation. Meanwhile, we show a concise inequality criterion for decomposing qubit mixed states. The new results include previous ones as special cases. Our model and method may be applied to solve similar problems in high-dimensional and multipartite scenarios, Comment: comments are welcome

We study the quantum information masking based on isometric linear operators that distribute the information encoded in pure states to the correlations in bipartite states. It is shown that a isometric linear operator can not mask any nonzero measure set of pure states. We present a geometric characterization of the maskable sets, and show that any maskable set must be on a spherical circle in certain Euclidean spaces. Detailed examples and potential applications in such as secret sharing and quantum cryptography are analyzed., 7 pages, 3 figures, comments are welcome!

Masking of quantum information spreads it over nonlocal correlations and hides it from the subsystems. It is known that no operation can simultaneously mask all pure states [Phys. Rev. Lett. 120, 230501 (2018)], so in what sense is quantum information masking useful? Here, we extend the definition of quantum information masking to general mixed states, and show that the resource of maskable quantum states are far more abundant than the no-go theorem seemingly suggests. Geometrically, the simultaneously maskable states lays on hyperdisks in the state hypersphere, and strictly contain the broadcastable states. We devise a photonic quantum information masking machine using time-correlated photons to experimentally investigate the properties of qubit masking, and demonstrate the transfer of quantum information into bipartite correlations and its faithful retrieval. The versatile masking machine has decent extensibility, and may be applicable to quantum secret sharing and fault-tolerant quantum communication. Our results provide some insights on the comprehension and potential application of quantum information masking., Comment: 5+11 pages, 4+5 figures. To appear in PRL

We study the problem of information masking through nonzero linear operators that distribute information encoded in single qubits to the correlations between two qubits. It is shown that a nonzero linear operator cannot mask any nonzero measure set of qubit states. We prove that the maximal maskable set of states on the Bloch sphere with respect to any masker is the ones on a spherical circle. Any states on a spherical circle on the Bloch sphere are maskable, which also proves the conjecture on maskable qubit states given by Modi et al. [Phys. Rev. Lett. 120, 230501 (2018)]. we provide explicitly operational unitary maskers for all maskable sets. As applications, different protocols for secret sharing are introduced., 6 pages, 3 figures

In a recent paper, M. F. Sacchi [Phys. Rev. A 96, 042325 (2017)] addressed the general problem of approximating an unavailable quantum state by the convex mixing of different available states. For the case of qubit mixed states, we show that the analytical solutions in some cases are invalid. In this Comment, we present complete analytical solutions for the optimal convex approximation. Our solutions can be viewed as correcting and supplementing the results in the aforementioned paper., Comment: 4 pages, 2 figures

We investigate quantum information masking for arbitrary dimensional quantum states. We show that mutually orthogonal quantum states can always be served for deterministic masking of quantum information. We further construct a probabilistic masking machine for linearly independent states. It is shown that a set of d dimensional states, $\{ |a_1 \rangle_A, |t a_2 \rangle_A, \dots, |a_n \rangle_A \}$, $n \leq d$, can be probabilistically masked by a general unitary-reduction operation if they are linearly independent. The maximal successful probability of probabilistic masking is analyzed and derived for the case of two initial states., Comment: 5 pages, 1 figures

We explore quantum phase transitions in the spin-1/2 [Formula: see text] chain with three-spin interaction in terms of local quantum Fisher information and one-way quantum deficit, together with the demonstration of quantum fluctuations. Analytical results are derived and analyzed in detail.

We consider the optimal approximation of arbitrary qubit states with respect to an available states consisting the eigenstates of two of three Pauli matrices, the $B_2$-distance of an arbitrary target state. Both the analytical formulae of the $B_2$-distance and the corresponding complete optimal decompositions are obtained. The tradeoff relations for both the sum and the squared sum of the $B_2$-distances have been analytically and numerically investigated.

SAW sensing technology has advantages of wireless, passive, small size, low cost, fast response, strong anti-electromagnetic radiation, measurable for moving or rotating objects, tolerable for wet dirty or high temperature and other harsh environments. Comparing with the traditional sensing methods, the test of SAW sensing technology can cover almost all the needs of digital substation internet of things.

Electromagnetic Current Transformer (CT) is one of the main equipment in power system, and the remanence in the measuring or protective windings of CT will influence the stability of the power system. Measuring CT is mainly used for the electric energy measurement in normal working condition, focusing on the steady operation state; while protective CT is usually used in fault or short-circuit condition, and the transient transfer characteristic is of significant important. Considering high remanence operation environment in the power system, the numeric analytical model of CT, which is working in the saturation condition, is depicted in this paper. With analyzing the amount of exciting current caused by remanence and deducing the transfer characteristic of CT, the influence of the remanence on the relay protection and the corresponding precautions are proposed, providing accurate and reliable theoretical basis for the protective CT’s correct action and safety operation after system failure. Finally, the electromagnetic transient model of protective CT (TPY) is built in PSCAD, the simulation result of which shows the validity and practicability of the proposed model.

Electronic current transformer is one of the key equipment of intelligent substation and has a direct impact to the correct operation of relay protection devices. In order to accurately establish the dynamic response model of electronic current transformer, it is needed to extract electromagnetic parameters of Rogowski coil, which is the electromagnetic coupling part of electronic current transformer. This paper builds the electromagnetic parameters model and extracts the electromagnetic distribution parameters of Rogowski coil based on the finite element method, then we use the equivalent method to calculate the lumped electromagnetic parameter. At last, comparing with the experimental results, a good accuracy of the simulation results based on finite element method is presented.

Transient saturation characteristics of TPY-type current transformer have great impact on the right action of line differential protection. This paper proposes an analytical method of line differential protection under current transformer saturation by utilizing current transformer model and test methods. The true current value of primary side can be obtained by our proposed method and therefore it yields correct assessment of line operating status. This method has high reliability applying to practical engineering examples of differential protection.

This paper presents the numerical modeling of a classical switched reluctance motor (SRM) and a mutually coupled SRM (MCSRM); both have three phases with 12 slots and 8 poles. The multiphysics models have been developed, which can take into account the electromagnetic characteristics, mechanical vibration, and acoustic noise of the foregoing machines. A 2-D electromagnetic model has been used to calculate the magnetic force which is the main source of vibration of the entire motor system. The vibration of the motor is calculated by a mode superposition method, while the acoustic noise is predicted by a 3-D finite-element acoustic model. In order to validate the numerical models, experiments have been carried out. A good agreement between measured and numerical results has been observed, and it is found that the vibration and the noise levels of MCSRM are considerably lower than those of classical SRM.

The structure of the power tunnel is unique as a special place. It is built under the surface of the earth crust,belongs to half-hidden project. In recent years, affected by operating life, geological conditions, design and construction, the number of the tunnels which has structural safety risks apears more and more, so the safety of the tunnel structure always has been a very important issue of construction, operation and maintenance. This paper presents a tunnel structure safety monitoring system based on BOTDA technology.This system has good adaptability to the scene, and can remotely monitor the structural safety of the tunnel in real time, and it also has advantages of distribution, long-distance, high-precision, etc.

This paper describes FBG sensing demodulation technology which based on acousto-optic tunable filter, this technique solves the traditional FBG demodulation technique existing some problems such as slow demodulation speed and small number of driving FBG sensors. The demodulation technique has advantages with simple structure, low cost, wide wavelength range, high resolution and fast demodulation speed.

Temperature is an important operating parameter of electrical equipment, electrical equipment operating condition obtained by monitoring the temperature information has become research focus for power system fault prediction and diagnosis[1-. Distributed fiber optic temperature measurement system is a method for real-time measurement of the spatial distribution of temperature field sensing system. The system uses optical time domain reflectometer (OTDR) and laser Raman spectroscopy, amplifies temperature information and processes signal from wavelength division multiplexer and optical detectors, then the temperature information is displayed in real time[4-. Distributed fiber optic temperature measurement technology has several characteristics with insulation, anti-electromagnetic interference, resistance to high voltage, resistance to chemical corrosion, and security[6-. This article outlines the basic power system temperature monitoring content, studies the current distributed optical fiber temperature measurement technology applications in power system and prospects for its development trend.

The terahertz technology involves electromagnetics, semiconductor physics, optoelectronics, materials science and micro-processing technology and other disciplines. Based on terahertz technology, non-destructive testing has important research value and application prospect in the field of medical imaging, security checking, product testing and power system monitoring. The generation of terahertz technology and its advantages is described in this article, and an analysis is also given on the application of non-destructive testing based on terahertz technology in the field of smart grid such as cable accident warning, intelligent anti-theft system and electronic components monitoring.

Since the Aha Lake, located in Guizhou Province, China, was enlarged in 1982, a great amount of iron and manganese were input into it owing to the uninterrupted pollution from acidic mining drainage of coal mines (AMD). The results show that dissolved Fe2+ and Mn2+, mainly from AMD, were markedly separated each other as water flowed from inlet to downstream. The Aha lake water, with the average pH equal to 7.28, was not acidified just because the lake is developed in the karst area and people continuously put lime in it in recent years. Fe2 + and Mn2 + deposit in the different locations in lake because of the difference of oxidizing rate between Fe2+ and Mn2+ during water flowing from inlet to downstream, and also forming the horizontal separation along the lake water flowing direction. Manganese tends to be obviously enriched in the upper of sediment in lake's deep locations, presenting the remarkable separation with iron in the vertical section. After normalized by Ti content in sediment, it is obvious that the remarkable separation between iron and manganese corresponds with the enlargement of lake in 1982. As shown in the concentration profile of pore water in sediment, iron was remobilized weakly while manganese reduction mainly happens in the upper of sediment, indicating its strong remobilization. Based on the studies, a mechanism for environment and fractionation of Fe2+ /Mn2 + during water flowing in the lake was also demonstrated.

In this paper,assuming X is Banach and L is a finite codimension subspace of X. Application of the dual method,there obtain the formula of distance and elements of best approximation from given a point to the subspace of finite codimension under some condition,and apply the formula to solve some of the specific optimal control problem.