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Based on the theoretical mechanism analysis of FDI, regional innovation, and green economic efficiency, this article uses China’s provincial panel data to calculate the provincial green economic efficiency level based on the three-stage DEA method and uses the system GMM model, intermediary effect model, and threshold model to empirically test the specific effects and transmission paths of FDI on the efficiency of the green economy. Research shows that FDI is one of the important factors that promote the improvement of green economic efficiency. Subregional tests have found that FDI has a significant regional heterogeneity in promoting the efficiency of the green economy. The mediation effect test found that the mediation effect of regional innovation is significant, and FDI can significantly promote the growth of green economic efficiency through regional innovation. The threshold effect analysis found that there are significant and effective double thresholds for regional economic levels, and the impact of FDI on green economic efficiency is heterogeneous within different threshold intervals. The research conclusions provide new inspiration for China to allocate FDI more rationally and efficiently under the new development pattern.

Ardehali (Phys. Rev. A, 46, 5375 (1992). 10.1103/PhysRevA.46.5375) derived a Bell-type inequality for an n-particle system in a Greenberger–Horne–Zeilinger (GHZ) state. This inequality helps relax ...

This paper uses WIOD data to calculate and analyze the dominant comparative advantage of Chinese manufacturing global value chain (GVC) based on the WWZ method and empirically studies the influence of digitization on the competitiveness of manufacturing GVC. The main findings are as follows: (1) The competitiveness of Chinese manufacturing GVC has been improved as a whole. The GVC competitiveness of different types of industries is quite different: GVC in middle- and low-knowledge-intensive industries have the highest competitiveness, while those with middle- and high-knowledge-intensive industries have the lowest competitiveness and apparent shortboard industries. (2) Digitization is conducive for enhancing the competitiveness of manufacturing GVC. In terms of industries, digitization has a significant positive effect on the GVC competitiveness of middle and high-knowledge-intensive industries but not on low knowledge ones. As for the sources of digital input, the positive effect is more outstanding. Also, it is more remarkable when it comes to the software and information technology service industry. (3) As for the mechanism of action, labor productivity is an effective way to improve the manufacturing GVC competitiveness digitally. Finally, after a robustness test, the positive effect of the digital input remains robust.

Quantum correlations of higher-dimensional systems are an important content of quantum information theory and quantum information application. The quantification of quantum correlation of high-dimensional quantum systems is crucial, but difficult. In this paper, using the second-order nonlinear optical effect and multiphoton interference enhancement effect, we experimentally implement the photonic qutrit states and demonstrate the spin-1 information entropic inequality for the first time to quantitative quantum correlation. Our work shows that information entropy is an important way to quantify quantum correlation and quantum information processing.

Arpan Das et al. proposed a set of new Bell inequalities (Das et al., 2017 [16] ) for a three-qubit system and claimed that each inequality within this set is violated by all generalized Greenberger–Horne–Zeilinger (GGHZ) states. We investigate experimentally the new inequalities in the three-photon GGHZ class states. Since the inequalities are symmetric under the identical particles system, we chose one Bell-type inequality from the set arbitrarily. The experimental data well verified the theoretical prediction. Moreover, the experimental results show that the amount of violation of the new Bell inequality against locality realism increases monotonically following the increase of the tangle of the GGHZ state. The most profound physical essence revealed by the results is that the nonlocality of GGHZ state correlate with three tangles directly.

Knowing the level of entanglement robustness against quantum bit loss or decoherence mechanisms is an important issue for any application of quantum information. Fidelity of states can be used to judge whether there is entanglement in multi-particle systems. It is well known that quantum channel security in QKD can be estimated by measuring the robustness of Bell-type inequality against noise. We experimentally investigate a new Bell-type inequality (NBTI) in the three-photon Greenberger–Horne–Zeilinger (GHZ) states with different levels of spin-flip noise. The results show that the fidelity and the degree of violation of the NBTI decrease monotonically with the increase of noise intensity. They also provide a method to judge whether there is entanglement in three-particle mixed states.

Because of its important role both in fundamental theory and applications in quantum information, evolution of entanglement in a quantum system under decoherence has attracted wide attention in recent years. In this paper, we experimentally generate a high-fidelity maximum entangled two-qubit state and present an experimental study of the decoherence properties of entangled pair of qubits at collective (non-collective) bit-flip and phase-shift noises. The results shown that entanglement decreasing depends on the type of the noises (collective or non-collective and bit-flip or phase-shift) and the number of qubits which are subject to the noise. When two qubits are depolarized passing through non-collective noisy channel, the decay rate is larger than that depicted for the collective noise. When two qubits passing through depolarized noisy channel, the decay rate is larger than that depicted for one qubit.

Using two-step growth method and buffer layer annealing treatment, the double heterojunction structures of In0.82Ga0.18As epilayer capped with InAs0.6P0.4 layer were prepared on InP substrate by low pressure metal organic chemical vapor deposition (LP-MOCVD). Based on the high quality In0.82Ga0.18As structures, the In0.82Ga0.18As PIN photodetector with cut-off wavelength of 2.56 μm at room temperature was fabricated by planar semiconductor technology, and the device performance was investigated in detail. The typical dark current at the reverse bias V R=10 mV and the resistance area product R 0 A are 5.02 μA and 0.29 Ω·cm2 at 296 K and 5.98 nA and 405.2 Ω·cm2 at 116 K, respectively. The calculated peak detectivities of the In0.82Ga0.18As photodetector are 1.21×1010 cm·Hz1/2/W at 296 K and 4.39×1011 cm·Hz1/2/W at 116 K respectively, where the quantum efficiency η=0.7 at peak wavelength is supposed. The results show that the detection performance of In0.82Ga0.18As prepared by two-step growth method can be improved greatly.

Using the entangled two-photon systems, we experimentally demonstrate the predictions of the analog Clauser-Horne- Shimony-Holt (CHSH) inequality and investigate the robustness of the CHSH-class inequality in the bit-flip noisy environment. We obtain the experimental results of CHSH inequality and analog CHSH inequality as S CHSH=2.64±0.02 and S analogCHSH=2.76±0.02, respectively, and prove that the analog CHSH inequality is more robust against bit-flip noise than the CHSH inequality. It provides better advantages for the experimental study and application.

In this paper, by using the second-order parametric down-conversion of the nonlinear crystal, the spin-1 state is simulated by the two-photon polarization entangled modes. Through adjusting the laser pulse power density, the efficiency of second-order parametric down-conversion is enhanced. The intensity of the spin-1 state is 0.5/s. The fidelity of the state is up to F=0.891±0.002, and the contrast is C=17.3. The results provide a new method for Stern-Gerlach measurement on the spin-1 system.

Entanglement and decoherence are two intimately related phenomena that lie at the heart of quantum information. The EPR-Bell states are the most basic quantum systems, which form the complete entangled basis of the two-particle Hilbert space, and which are important in many quantum computation schemes. The bit flip, phase flip, and bit-phase flip noise channels represent all the possible errors in quantum computation. Thus, the quantum decoherence characteristic of maximally and partially Bell entangled states under different noisy channels is studied using the concurrence. Our work is useful for linear-optical quantum computation and quantum communication schemes whose building blocks are entangled state.

By exploiting both the photons’ polarization and spatial degrees of freedom, we experimentally demonstrate a hyper-entangled four-photon six-qubit Greenberger-Horne-Zeilinger (GHZ) state. Based on the state, we experimentally test the multi-particle Ardehali inequality and prove the theoretical prediction of Ardehali. Furthermore, we experimentally first investigate the robustness of the Ardehali inequality for the four-photon six-qubit GHZ state in a bit-flip noise environment and show the good robustness against decoherence for this inequality. Our works provide an experimental benchmark to estimate the safety of quantum channel in the noisy environment.

Using spontaneous parametric down conversion, polarization post selection and coincidence counting technique, the polarization Einstein-Podolsky-Rosen (EPR) entangled states are prepared. Experimental studies on the efficiency, contrast and fidelity with different pump laser intensities are performed systematically. The results show that the pump laser intensity distinctly influences the quality of entangled photons, especially the contrast and the fidelity. On the other hand, the pump efficiency of entangled photons is almost invariable, namely the entangled source brightness increases linearly with the increase of pump laser power.

Room- and variable-temperature photoluminescence from 3C-SiC aloetic-shaped nanowires was presented. The SiC nanowires were prepared on Si(100) substrates by the reaction of methane with silicon dioxide. Scanning electron microscope (SEM) and X-ray diffraction (XRD) are used to characterization the nanowires. A green photoluminescence (PL) band centered at 2.34 eV is observed in the nanowires at room temperature. The results from variable-temperature photoluminescence show anomalous temperature dependencies of the spectral characteristics. The emission intensity increases with decreasing temperature until reaching an intensity maximum at about 155 K, then it decreases at lower temperatures. The emission energy has little shift following temperature variations. The anomalous temperature dependencies of PL results may be explained by quantum confinement effect and phonon participation in the emission process.

A simple and effective method is developed to controllably synthesize branching silicon carbide (SiC) nanowires by using gas flow fluctuation. The experimental results indicated that uniformly 'Y' shaped branching SiC nanowires were successfully synthesized. A branching mechanism of fluctuation-promoted split of catalyst particles is proposed. The synthetic approach presented here will open a new route to fabricate other nanomaterials branching structure. Photoluminescence (PL) spectrum and mapping result show that the nanowires can emit green band centered at 2.32 eV (535 nm) at room temperature, indicating potential applications in integrated nano–optoelectronic devices.

In this paper the Fisher information of Gaussian pure States is studied. Based on the definition of joint non-classical properties, we calculate the non-classical properties of Gaussian pure States. The results show that the Fisher information and Fisher length are efficacious tools to study the non-classical properties of quantum States.

We investigate theoretically and experimentally the tripartite entanglement defined by V. Coffman [Phys. Rev. A 61 (2000) 052306] and nonlocality expressed by the Mermin inequality [Phys. Rev. Lett. 65 (1990) 1838] in three-qubit generalized Greenberger–Horne–Zeilinger (GGHZ) states. Using our GGHZ states with fidelity ∼0.84, we demonstrate experimentally the theoretical results of tripartite entanglement and the Mermin theorem successfully. It is shown that the experimental results are in good agreement with the theoretical predictions.

A new simple method was developed to synthesize silica nanowires by physical thermal evaporation of a mixture of silica particles and iron trichloride. The silica nanowires have diameters from 30 to 50 nm, and lengths of ~10 μm, with iron particles at their tips. The growth mechanism of the amorphous silica nanowires follows vapor–liquid–solid model. A broad blue–green photoluminescence band with defined maximum peak energy of ~2.45 eV is observed at room temperature revealing that the silica nanowires could have potential applications in optoelectronic devices.

We experimentally characterized a high-intensity optical three-qubit Greenberger–Horne–Zeilinger (GHZ) states with a count of ∼ 25 / s by using the method of over-complete state tomography. Furthermore, based on the state, a convincing, 3.5 standard deviations, violation of Gisinʼs inequality has been measured, thus confirming the validity of Gisinʼs inequality for three-qubit GHZ states. From the data, we verified the good agreement of the experimental violation with the value predicted by quantum mechanics given the reconstructed density matrix. This result represents the first step towards the experimental implementation of Gisinʼs theorem.

In this paper, we discuss a microscopic model for the detector-field system in the theory of the quantum counting process. The detector-field system is described by a generalized Jaynes–Cummings model, from which we derive an analytic expression of the general quantum jump superoperators. To illustrate the universality and convenience of our method, we consider two specific examples with the help of the analytic expression.

In the framework of thermo-field dynamics, invented by Umezawa et al., we construct a mixed coherent state representation of density operator ρ. This new representation is useful because it provides an approach to retrieve ρ from its c-number solution of master equations in the entangled state representation.

In this paper, we have studied the dynamics of nonlocality for a hybrid entangled state in a thermal reservoir. The density operator of the system is obtained by using a superoperator method. The dynamics of nonlocality for the mixed hybrid entangled state is uncovered by using the Bell operator based on the 'pseudospin operator' for a light field (Chen Z B, Pan J W, Hou G and Zhang Y D 2002 Phys. Rev. Lett. 88 040406). The dynamics of nonlocality has also been studied using other Bell operators.

A systematic approach to integrate the Heisenberg equations of motion is proposed by using the Weyl-ordered polynomials. The solutions of the Heisenberg equations of motion, i.e. P(t) and Q(t), are expanded as a sum over the Weyl-ordered polynomials Tm,n(P(t),Q(t)) at time t = 0. The coefficients of the expansions satisfy two sets of first-order ordinary differential equations resulting from the Heisenberg equations of motion for time-independent systems. This general approach for time-independent systems is also tractable in obtaining the adiabatic invariants of the time-dependent systems. In this paper, interest is mainly focused on the formal aspect of the approach.

Using the decomposition theorm of superoperators, an explicit solution of the master equation for an attenuated or amplified nonlinear oscillator is presented. It is found that the time evolution of the density operator can be easily obtained from an arbitary initial state using this method.

We construct a general supersymmetric quantum transformation for studying the supersymmetric quadratic Hamiltonian which contains the interaction of multi-mode fermions with multi-mode bosons. The Hamiltonian can be derived from that of multi-mode radiation field interacting with m two-level atoms. By using the supersymmetric quantum transformation, the diagonolized Hamiltonian is given. We also concisely derive the analytic expression of the super-partition function for the supersymmetric quadratic Hamiltonian without knowing the energy spectrum.

The highest qubit Ardehali inequality violation with 203 standard deviations is first experimentally demonstrated using the hyper-entangled four-photon-eight-qubit Greenberger-Horne-Zeilinger (GHZ) state. Moreover, we experimentally investigate the robustness of the Ardehali inequality for the four-, six-, and eight-qubit GHZ states in a rotary noisy environment systematically. Our results first validate the Ardehali' theoretical statement of relation between violation of Ardehali inequality and particle number, and proved that Ardehali inequality is more robust against noise in larger number qubit GHZ states, and provided an experimental benchmark for us to estimate the safety of quantum channel in the noisy environment.

The multiphoton Jaynes–Cummings model is theoretically generalized to the simplest case of collectively radiating atoms. For this Jaynes–Cummings model, we find its supersymmetric structure. Based on this, we introduce a supersymmetric unitary transformation to diagonalize the Hamiltonian, and in so doing, its eigenvalues and eigenfunctions are obtained. Some transition processes are calculated.

There are different families of inequalities that can be used to characterize the entanglement of multiqubit entangled states by the violation of quantum mechanics prediction versus local realism prediction. In a noisy environment, the violation of different inequalities distinguishes a direct from a noise-free environment. That is, each inequality has a different robustness against noise. We investigate theoretically and experimentally this proposition with the Mermin inequality, Bell inequality, and Svetlichny inequality using three-qubit GHZ states for different levels of noise. Our purpose is to determine which one of the inequalities is more robust against noise and thus more suitable to characterize entanglement of states. Our results show that the Mermin inequality is the most robust against stronger noise and is, thus, more suitable for characterizing the entanglement of three-qubit GHZ states in a noisy environment.

As stated by S. Ghose et al. [Phys. Rev. Lett. 102, 250404 (2009)], there are certain relationships between tripartite entanglement and tripartite nonlocality for three-qubit Greenberger-Horne-Zeilinger (GHZ) class states. In the present work, we have experimentally demonstrated the theoretical results of Ghose et al. by using both three-photon generalized GHZ (GGHZ) states and maximal slice (MS) states with a count of $\ensuremath{\sim}$10/s. From the data, we have verified the agreement of the experimental violation of the Svetlichny inequality with the one predicted by quantum mechanics given the reconstructed density matrix. For the MS states, it is demonstrated that the amount of violation increases linearly following the increase of the degree of tripartite entanglement. In contrast, for GGHZ states, there is a minimal value of the violation when the degree of tripartite entanglement is 1/3. Both of the results are consist with the theoretical prediction.

We experimentally realize a high-intensity three-photon Greenberger-Horne-Zeilinger (GHZ) entanglement source directly following the proposal by Rarity and Tapster [J. G. Rarity and P. R. Tapster, Phys. Rev. A 59, R35 (1999)]. The threefold coincidence rate can be more than 200 Hz with a fidelity of 0.811, and the intensity can be further improved with moderate fidelity degradation. The GHZ entanglement is characterized by testing the Bell-Mermin inequality and using an entanglement witness operator. To optimize the polarization-entangled source, we theoretically analyze the relationship between the mean photon number of the single-photon source and the probability of parametric down-conversion., Comment: 4 pages, 4 figures

In this paper, using the decomposition theorem of superoperators, we present a general method to solve master equations with superoperator generators of su(1,1) and su(2) Lie algebras. With the help of this method, the time evolution of the density operators for certain systems, which have SU(1,1) and SU(2) symmetry, can be easily obtained from any given initial state.