Direction Of Steering Research Articles

Manipulating one-way quantum steering in a mechanical gain-loss optomechanical system

Based on the phenomenon of exceptional points (EPs) in the optomechanically induced mechanical PT-symmetric binary and ternary systems, we propose a mechanism to generate the perfect one-way quantum steering between two totally symmetric modes, respectively. By investigating the quantum steering behavior in the close vicinity of EP, we find that the optimal one-way quantum steering can be successfully generated at the EP in the PT-symmetric binary mechanical system. When pushing the system towards the EP, we show that not only is the broadest region of the one-way quantum steering achieved, but the robustness against the thermal noise can be significantly enhanced. In addition, the direction of the one-way quantum steering can be precisely controlled only by altering the sign of the detuning of the cavity field. What’s more, we analyze the mean populations of the involved modes to further support our findings and find that the occurrence of the one-way quantum steering depends mainly on the difference in the populations between the two target modes. We also successfully extend our findings to the high-order EP, and the desired one-way quantum steering can still be generated in the PT-symmetric ternary mechanical system when it operates at the EP. Our scheme opens up an alternative manipulation method to explore the various novel quantum effects exploiting the EPs and has significant potential applications in quantum nonreciprocal devices.

NEW DESIGN OF SPRING-HYDRAULIC SUSPENSION OF VEHICLE WHEELS

The designs of independent suspensions of vehicle wheels (single-lever with levers of equal thickness, double-lever with levers of different lengths, lever-telescopic, double-lever with torsion bar) are considered. The complexity of suspension structures and their low reliability in conditions of poor cross-country is noted. The ensures stabile damping efficiency in any direction of movement and comfortable steering. The absence of a complex lever system in the suspension design increases its reliability.

Manipulating the direction of one-way steering in an optomechanical ring cavity

Quantum steering refers to the apparent possibility of exploiting nonseparable quantum correlations to remotely influence the quantum state of an observer via local measurements. Different from entanglement and Bell nonlocality, quantum steering exhibits an inherent asymmetric property, which makes it relevant for many asymmetric quantum information processing tasks. Here, we study Gaussian quantum steering between two mechanical modes in an optomechanical ring cavity. Using experimentally feasible parameters, we show that the state of the two considered modes can exhibit two-way steering and even one-way steering. Instead of using unbalanced losses or noises, we propose a simple practical way to control the direction of one-way steering. A comparative study between the steering and entanglement of the studied modes shows that both steering and entanglement undergo a sudden death-like behavior. In particular, steering is found more fragile against thermal noise remaining constantly upper-bounded by entanglement. The proposed scheme may be meaningful for one-sided device-independent quantum key distribution, where the security of such protocol depends fundamentally on the direction of steering.

Reliable experimental manipulation of quantum steering direction.

Noise-adding methods have been widely used to manipulate the direction of quantum steering, but all related experimental schemes only worked under the assumption that Gaussian measurements were performed and ideal target states were accurately prepared. Here, we prove, and then experimentally observe, that a class of two-qubit states can be flexibly changed among two-way steerable, one-way steerable and no-way steerable, by adding either phase damping noise or depolarization noise. The steering direction is determined by measuring steering radius and critical radius, each of which represents a necessary and sufficient steering criterion valid for general projective measurements and actually prepared states. Our work provides a more efficient and rigorous way to manipulate the direction of quantum steering, and can also be employed to manipulate other types of quantum correlations.

Three-color and tripartite steering generated by intracavity cascaded processes

Einstein–Podolsky–Rosen (EPR) steering has important practical applications in secure quantum communication because of its unique characters. Multicolor and multipartite EPR steering is an important resource for connecting different physical systems in the quantum networks with several nodes. We investigate three-color and tripartite steering properties based on the intracavity cascaded nonlinear processes of down conversion and sum frequency. Based on the criteria proposed by Kogias [Phys. Rev. Lett. 114, 060403 (2015)], the steering parameters among down-conversion fields and sum-frequency field versus the normalized frequency and the pump parameter are studied. Our research shows that the direction of steering and steerability can be manipulated flexibly. We also show that quantum secret sharing can be realized in our scheme. And the results of asymmetric quantum steering and joint quantum steering among different modes provide a technical reference for the construction of secure quantum information network.

Manipulation and enhancement of Einstein-Podolsky-Rosen steering between two mechanical modes generated by two Bogoliubov dissipation pathways

We consider a three-mode optomechanical system in which two mechanical oscillators are independently coupled to a cavity mode driven by two controllable lasers. By controlling the two-tone driving, one can prepare the entanglement and Einstein-Podolsky-Rosen (EPR) steering of two mechanical modes, in which the cavity mode acts as a single reservoir to cool two Bogoliubov modes. We find that the direction of EPR steering can be manipulated effectively by adjusting the damping rates and the thermal noises of two mechanical modes. In addition, we show that the entanglement and EPR steering between two mechanical modes can be enhanced by adding a parametric amplifier (PA) into the cavity. The effects of the strength and phase of the PA on the mechanical entanglement and EPR steering are analyzed and discussed in detail. Meanwhile, the additional PA can also expand the region of the one-way steering and strengthen the robustness of the entanglement and EPR steering against the thermal noise. The present scheme may provide effective resources for quantum information processing.

Enhancement of mechanical entanglement and asymmetric steering with coherent feedback

We propose a scheme to enhance entanglement and asymmetric steering between two mechanical oscillators in an optomechanical system with coherent feedback control. In the system, an optical cavity interacts with two mechanical oscillators and an auxiliary cavity whose output field is fed back into the input port of the optical cavity via a feedback loop. Due to the coherence between the auxiliary cavity and feedback, we derive the effective decay rate and a nonzero frequency shift of the optical cavity. Consequently, the induced beam-splitter-type and parametric-type interactions between the two mechanical oscillators are modulated, which leads to the enhancement of entanglement and the generation of asymmetric steering even if the two mechanical oscillators possess identical decoherence properties. And the direction of asymmetric steering can be controlled by tuning the jumping phase between two cavities and optimizing the ratio of drive asymmetry. In contrast to the method of adding losses or noises to one subsystem at the cost of reducing steerability, this scheme provides an active way to achieve enhanced asymmetric steering. Furthermore, the steady-state and dynamical entanglement and asymmetric steering can be generated in the unresolved-sideband regime, which is friendly for experimental implementation.

Do Heterogeneous Environmental Policies Improve Environmental Quality While Promoting Economic Growth?

The long-standing model of high energy consumption growth of China has put the country at a market disadvantage in terms of clean technological innovation and clean goods production. With the support of national policies, China’s environmental industry has achieved rapid development. However, the key to establishing a long-term effective mechanism is how to encourage enterprises to develop and use green and clean technologies. Thus, we construct a theoretical model related to environmental policies and then derive the impact of heterogeneous environmental policies on different research and development (R&D) approaches. The environmental and economic effects of heterogeneous environmental policies are then explored by incorporating environmental quality and economic growth into the model. Next, we evaluate the policy effect based on the panel data of prefecture-level cities in China from 2009 to 2016. In a further discussion, we measure the decoupling indices of carbon emissions and economic growth for each of the 281 prefecture-level cities in China using the Tapio model. Through theoretical derivation and empirical analysis, this paper provides a more comprehensive study of the green bias effect of environmental policies. The results show that environmental policies can significantly promote green technological innovation regardless of the R&D approach adopted by firms. The difference is that when firms conduct their own R&D, the sector’s R&D efficiency parameters determine the direction of technological innovation steering. When technological innovation is introduced externally, the substitution relationship between sectoral products determines whether environmental policy is effective. Finally, the combination of environmental regulation and government subsidies is more effective in green-biasing technological innovation.

Entanglement and Asymmetric Steering Between Distant Magnon and Mechanical Modes in an Optomagnonic‐Mechanical System

AbstractA scheme is proposed to generate long‐distance entanglement and asymmetric steering between mechanical oscillator and magnon mode across the frequency difference of ≈10 GHz in an optomagnonic‐mechanical system composed of a magnon, a mechanical oscillator, and two cavities. The calculated results reveal that the long‐distance magnon–phonon entanglement can be achieved due to the fact that the quantum correlation of the two‐mode squeezed vacuum microwave field is successively transferred to the magnon mode and the phonon mode. Moreover, the entanglement is strong enough such that the quantum steering between magnon mode and phonon mode can be achieved in an asymmetric manner. Furthermore, the direction of quantum steering can be flexibly adjusted via changing the magnon damping rate, coupling strength, squeezing parameter, and bath temperature. The proposed scheme provides the possibility for the generation of macroscopic quantum entanglement and steering and has potential applications in quantum information processing.

Manipulating the quantum steering direction with sequential unsharp measurements

Quantum steering exhibits an inherent asymmetric property that differs from both quantum entanglement and Bell nonlocality, which leads to no-way, one-way, and two-way steering. Flexibly manipulating the direction of quantum steering without reducing the quantum steerability is very important for information processing. In this paper, implementing sequential unsharp measurements and the steering-radius criterion, we show how to manipulate that steering direction among multiple Alices and Bobs. We demonstrate that the change in steering direction depends on the number of measurement settings and the sharpness of measurements. For a given two-qubit asymmetric state, we obtain 13 kinds of steering regions with different steering directions in the case of one Alice and three Bobs and obtain 11 kinds in the case with two Alices and two Bobs. For the case with one Alice and three Bobs, we further find a volume bound to visualize quantum steering. Our manipulation scheme is experimentally easy to achieve and rather assigns the steerability to more observers without reducing it, which offers a direct reference for the practical application of quantum steering.

Asymmetric Quantum Steering Generated by Triple-Photon Down-Conversion Process With Injected Signals

Asymmetric quantum steering generated by the triple-photon down-conversion process in an injected signal optical cavity is investigated. The triple-photon down-conversion process can be realized in an optical superlattice by quasi-phase-matching technology. Asymmetric quantum steering can be obtained in this triple-photon down-conversion process. The direction of asymmetric quantum steering can be controlled by adjusting the parameters of the nonlinear process. The generation of asymmetric quantum steering in the present scheme has potential applications in quantum secret sharing and quantum networks.

Einstein-Podolsky-Rosen steering and monogamy relations in controllable dynamical Casimir arrays

We achieve the controllable multipartite Einstein-Podolsky-Rosen (EPR) steering and its monogamy relations by means of the dynamical Casimir effect in the frame of superconducting quantum network. We employ the external driving flux of the superconducting quantum interference device as a switch. It is interesting that the system exhibits different types of the EPR steering and monogamy relations by tuning parameters. In the system, the one-way or two-way EPR steerings for different parties have been realized, and the direction of the one-way EPR steering is reversed by tuning coupling parameters. Remarkably, we can also obtain the EPR steering orderly sudden death for different modes. In addition, the system not only shows the type-I and type-II monogamy relations, but also converts steering parties to get monogamy relations' swapping and cycling. Finally, we discuss the influence of temperature. In the system, the higher the temperature is, the earlier sudden death for the EPR steering is. These results are important for quantum information and lay a foundation for us to better understand the important role of the multipartite EPR steering in secure quantum communication.

Asymmetric steerability of quantum equilibrium and nonequilibrium steady states through entanglement detection

Einstein-Podolsky-Rosen steering describes a quantum correlation in addition to entanglement and Bell nonlocality. However, conceptually different from entanglement and Bell nonlocality, quantum steering has an asymmetric definition. Motivated by the asymmetric definition of quantum steering, we study the steerability of two interacting qubits, which have asymmetric energy levels, coupled with asymmetric environments. The asymmetric (nonequilibrium) environments are two environments with different temperatures or chemical potentials. The Bloch-Redfield equation is applied to study the dynamics of two qubits and its long-time behavior. In our study, the steady-state steerability is determined by an experimentally friendly steering criteria, which demonstrates steering through the entanglement detection. Our results show that the steady states of two asymmetric qubits have the advantage for one direction of steering, compared to the symmetric setup. We also provide analytical results on the minimal coupling strength between the two qubits in order to be steerable. The asymmetric steerability is collectively determined by the nature of the two qubits and the influence from equilibrium or nonequilibrium environments. Nonequilibrium environments with the cost of nonzero entropy production can enhance the steerability in one direction. We also show the strict hierarchy of entanglement, steering, and Bell nonlocality of the nonequilibrium steady states, which shows a richer structure of steering than entanglement and Bell nonlocality.

Controlled Asymmetry of Einstein-Podolsky-Rosen Steering with an Injected Nondegenerate Optical Parametric Oscillator.

We propose and analyze a nonlinear optical apparatus in which the direction of asymmetric steering is controllable within the apparatus, rather than by adding noise to measurements. Using a nondegenerate parametric oscillator with an injected signal field, we show how the directionality and extent of the steering can be readily controlled for output modes that can be up to one octave apart. The two down-converted modes, which exhibit the greater violations of the steering inequalities, can also be controlled to exhibit asymmetric steering in some regimes.

Manipulating the direction of Einstein-Podolsky-Rosen steering

Einstein-Podolsky-Rosen (EPR) steering exhibits an inherent asymmetric feature that differs from both entanglement and Bell nonlocality, which leads to one-way EPR steering. Although this one-way EPR steering phenomenon has been experimentally observed, the schemes to manipulate the direction of EPR steering have not been investigated thoroughly. In this paper, we propose and experimentally demonstrate three schemes to manipulate the direction of EPR steering, either by varying the noise on one party of a two-mode squeezed state (TMSS) or transmitting the TMSS in a noisy channel. The dependence of the direction of EPR steering on the noise and transmission efficiency in the quantum channel is analyzed. The experimental results show that the direction of EPR steering of the TMSS can be changed in the presented schemes. Our work is helpful in understanding the fundamental asymmetry of quantum nonlocality and has potential applications in future asymmetric quantum information processing.

Impeller entrance pre whirl characteristics research

In order to study the effect of inlet port on the pump performance, the impeller inlet part, should be analyzed for impeller is able to extend the function of water flow to the front of the impeller for a long distance. Impeller flow of pre swirl flow is due to selection of least resistance into the impeller, but the pre swirl in the flow direction according to the impeller blade entrance angle, and the circumferential velocity of flow. The study found that lies in the external characteristic of the pump will be fell when the off-design, but in the case of large flow impeller and impeller in the direction of the front entrance fluid pre whirl steering is on the contrary, when this with little traffic is quite different .this article will study the occurrence, development, and the mechanism of the influence of flow field.

Numerical simulation of ultrasonic propagation and defect testing in laser cladding remanufacturing parts

The laser cladding remanufacturing parts show typical anisotropic behaviors, which is difficult for acoustic detection. Therefore, the propagation behaviors of ultrasonic beam in the laser cladding remanufactured parts should be investigated in-depth, which will provides an important theoretical basis for ultrasonic nondestructive evaluation of this kind of parts. An ultrasonic measurement model for the laser cladding remanufacturing parts was developed. The influence of anisotropic laser cladding coating on the propagation behaviors of ultrasonic beam was analyzed. The propagation behaviors of ultrasonic beam in the laser cladding Fe314 alloy coating were investigated with the help of Rayleigh integral combined with Pencil method. The simulation results show that the influence of anisotropic material on the incident field due to the value of slowness, the direction of beam steering is determined by the normal vector of slowness surface, the beam focusing and defocusing behavior is determined by the curvature of slowness surface. The radiated ultrasonic field maintains a uniform distribution relative to the axis of the incident beam, when the direction of incident beam is consistent with or perpendicular to the grain orientation of laser cladding coating, which the directivity of beam is preferably. The reason lies in the incident direction of ultrasonic wave is perpendicular to the isotropic plane of crystal. In the radiated field of transverse wave angle probe, the transverse wave splits and the beam steers, separates with the change of grain orientation. The fundamental reason that transverse wave splitting due to the anisotropy of the laser cladding coating. The reason that beam steering lies in that the direction of group velocity (the direction of normal vector of slowness surface) is inconsistent with that of phase velocity (the direction of transverse wave vector). The slowness surface of anisotropic laser cladding coating is irregular in shape, the beam will appear in other angles in addition to the main beam, when transverse wave refraction. An ultrasonic measurement model for the laser cladding remanufacturing parts was developed by combining the beam model with the scattering model based on Kirchhoff approximation and Born approximation theory. This model can be used to predict the testing signals from the flaws in laser cladding remanufacturing parts. The accuracy of the provided model was verified by comparisons of the simulation results with the experimental results, both the signal amplitude and phase were in good agreement. Numerical simulation results provide an important theoretical basis for rational design of the process scheme of ultrasonic testing for laser cladding remanufacturing parts.

Steering Angle Varied Pattern for Ultrasound Imaging with a Two-Dimensional Array

Methods and systems for varying a pattern as a function of steering angle for medical imaging with a multidimensional array are provided. Transmit waveform, delay, phase or apodization patterns in addition to delays, phases or apodization for focusing are used with a multidimensional array. By applying a periodic variation perpendicular to the steering direction, the effects of grating lobes due to the variation may be reduced. Along the steering direction, additional offsets are not provided, but may be provided. This different or non-existent offsets provide less grating lobe clutter. The transmit aperture is adjusted to be parallel to a direction of steering of non-normal transmit scan line or scan lines. The variation pattern is selected to result in enhancement or isolation of one or more frequency bands from one or more other frequency bands, such as isolation of second harmonic information from fundamental transmit frequency information.

BEAM STEERING AND FOCUSING ABILITY OF A CONTACT ULTRASOUND TRANSDUCER FOR TRANSSKULL BRAIN DISEASE THERAPY

This paper was to examine the steering and focusing ability of a contact hemispherical ultrasound transducer (80 mm radius of curvature, 160 mm diameter) for transskull brain diseases therapy without skull-specific aberration correction. This work employs a simulation program to investigate the effect of ultrasound transducer parameters on the steering and focusing ability for transskull therapy. The acoustic pressure distribution and the grating lobes in tissue were used to determine the steering and focusing ability of this transducer for a set of given conditions. Simulation results demonstrated that this hemispherical phased array transducer with low frequencies can steer a high-pressure focal zone in a large range within the brain. The peak and size of the high-pressure focal zone mainly depend on ultrasound frequency and the steering distance of the focal zone. By comparing the peak pressures between the focal zone and the grating lobe, 0.1 MHz transducer performed the desired results for large ranges (140 mm x-y direction and 138 mm z direction) of beam steering. The results reveal the feasibility of using a hemispherical phased array transducer with beam steering method at low frequency for brain diseases therapy within almost full range of the brain without performing a craniectomy.

PERFORMANCE OF AN ARRAY OF VERTICAL DIPOLES OVER AN INHOMOGENEOUS GROUND SYSTEM

The elevation radiation patterns of a stacked array of vertical electric dipoles (VEDs) over several different azimuthally symmetric inhomogeneous ground systems are studied using an integral formulation. As the ground influences the pattern of each VED differently, there is no known optimum array excitation which can be used to achieve desired beam shaping and steering. Patterns in an array of 21 VEDs spaced 0.1 lambda apart are computed and compared to HF (10 MHz) for three excitation functions: (a) conventional linear spacial phasing, (b) phasing according to the complex conjugate of the field produced by each VED in the direction of steering, and (c) spacially sinusoidal excitation with constant phasing. Results are given for grounds consisting of homogeneous earth, a perfectly conducting ground plane, a perfectly conducting disk on homogeneous earth and 2 lambda long radial wire ground systems on well- and poorly-conducting earth. It is found that the radiation pattern cannot be steered below about 9/sup 0/ in elevation for any of the excitation functions or the ground systems used. For low-angle steering conjugate excitation produces a slightly narrower beam with smaller sidelobes. Highly conducting grounds tend to permit steering to slightly higher elevations with narrower beams.