Classification of quantum correlation using deep learning.

Quantum correlation, as an intrinsic property of quantum mechanics, has been widely employed to test the fundamental physical principles and explore the quantum-enhanced technologies. However, such correlation would be drowned and even destroyed in the conditions of high levels of loss and noise, which drops into the classical realm and renders quantum advantage ineffective. Especially in low light conditions, conventional linear classifiers are unable to extract and distinguish quantum and classical correlations with high accuracy. Here we experimentally demonstrate the classification of quantum correlation using deep learning to meet the challenge in the quantum imaging scheme. We design the convolutional neural network to learn and classify the correlated photons efficiently with only 0.1 signal photons per pixel. We show that decreasing signal intensity further weakens the correlation and makes an accurate linear classification impossible, while the deep learning method has a strong robustness of such task with the accuracy of 99.99%. These results open up a new perspective to optimize the quantum correlation in low light conditions, representing a step towards diverse applications in quantum-enhanced measurement scenarios, such as super-resolution microscope, quantum illumination, etc.

Direct Observation of Dynamically Localized Quantum Optical States.

Quantum-correlated biphoton states play an important role in quantum communication and processing, especially considering the recent advances in integrated photonics. However, it remains a challenge to flexibly transport quantum states on a chip, when dealing with large-scale sophisticated photonic designs. The equivalence between certain aspects of quantum optics and solid-state physics makes it possible to utilize a range of powerful approaches in photonics, including topologically protected boundary states, graphene edge states, and dynamic localization. Optical dynamic localization allows efficient protection of classical signals in photonic systems by implementing an analogue of an external alternating electric field. Here, we report on the observation of dynamic localization for quantum-correlated biphotons, including both the generation and the propagation aspects. As a platform, we use sinusoidal waveguide arrays with cubic nonlinearity. We record biphoton coincidence count rates as evidence of robust generation of biphotons and demonstrate the dynamic localization features in both spatial and temporal space by analyzing the quantum correlation of biphotons at the output of the waveguide array. Experimental results demonstrate that various dynamic modulation parameters are effective in protecting quantum states without introducing complex topologies. Our Letter opens new avenues for studying complex physical processes using photonic chips and provides an alternative mechanism of protecting communication channels and nonclassical quantum sources in large-scale integrated quantum optics.

The salt secretion of leaves promotes the competitiveness of Reaumuria soongarica in a desert grassland.

BACKGROUND: For better understanding the mechanism of Reaumuria soongarica community formation in a salt stressed grassland ecosystem, we designed a field experiment to test how leaves salt secretion changes the competitive relationship between species in this plant communities. RESULTS: Among the three species (R. soongarica, Stipa glareosa and Allium polyrhizum) of the salt stressed grassland ecosystem, the conductivity of R. soongarica rhizosphere soil was the highest in five soil layers (0-55 cm depth). The high soil conductivity can increase the daily salt secretion rate of plant leaves of R. soongarica. In addition, we found the canopy size of R. soongarica was positively related to the distance from S. glareosa or A. polyrhizum. The salt-tolerance of R. soongarica was significantly higher than the other two herbs (S. glareosa and A. polyrhizum). Moreover, there was a threshold (600 µS/cm) for interspecific competition of plants mediated by soil conductivity. When the soil conductivity was lower than 600 µS/cm, the relative biomass of R. soongarica increased with the soil conductivity increase. CONCLUSIONS: The efficient salt secretion ability of leaves increases soil conductivity under the canopy. This leads the formation of a "saline island" of R. soongarica. Meanwhile R. soongarica have stronger salt tolerance than S. glareosa and A. polyrhizum. These promote the competitiveness of R. soongarica and inhibit interspecies competition advantage of the other two herbs (S. glareosa and A. polyrhizum) in the plant community. It is beneficial for R. soongarica to establish dominant communities in saline regions of desert grassland.

Photophysical and electrochemical properties of donor-acceptor conjugated oligomers based on 3,4-ethylenedioxythiophene and deficient rings.

The photophysical and electrochemical properties of four novel donor-accepter (D-A) conjugated oligomers a-d based on 3,4-ethylenedioxythiophene (EDOT) and electrondeficient heterocycle rings were investigated. The UV-vis absorption spectroscopy, fluorescence emission spectroscopy and cyclic voltammertry studies suggest that the oligomers are expected to provide enhanced charge-transporting properties for the development of efficient electroluminescent materials. Furthermore, the third-order nonlinear optical (NLO) measurements made by Z-scan technique indicate that they have good third-order NLO response and are desired materias for fabricating nonlinear photonic devices. In the solid state of these oligomers, a strong tendency of self-assembled structure was also revealed by X-ray diffraction (XRD) patterns in powder.

Significant effect of bromo substituents on nonlinear optical properties of polymer and chromophores.

Four chromophores containing bromo substituents, a ployimide with bromo-containing chromophores, four reference functional polyimides, and fourteen reference chromophores were synthesized for studying effect of bromo substituents on nonlinear optical (NLO) properties of materials and chromophores. The results of hyper-Rayleigh scattering and UV-vis spectra show that static first molecular hyperpolarizability (beta(0)) values of bromo-containing chromophores are 1.24-5.75 times as beta(0) of the corresponding chloro-containing chromophores (Hammett constants sigma of chloro and bromo groups are same) without causing a visible shift of the absorption band to longer wavelength. UV-vis spectra and the results of Maker Fringe method show that the polyimide with chromophores containing bromo substituents exhibits a good optical transparency and a much higher macroscopic nonlinear optical coefficient (d(33) = 20.1 pm/V) than the reference polyimides containing nitro (d(33) = 9.6 pm/V) and cyano (d(33) = 8.9 pm/V) groups in spite of nitro and cyano groups being strong electron acceptors. d(33) of polyimide with chloro-containing chromophores is very small. Therefore, this paper suggests an effective strategy for improving the NLO properties of polymeric materials and chromophores without reducing optical transparency in designing NLO polymers and chromophores. On the basis of quantum chemistry calculations, the reasons of effect of bromo substituents on NLO properties of chromophores and materials were discussed.

[Surface enhanced Raman scattering spectra of carbozole and azobenzene disperse red polymer].

Surface enhanced resonance Raman scattering (SERRS) was employed to study the molecule alignment of carbozole and azobenzene disperse red polymer on the surface of rough silver thin film. According to the selection rule of optical transitions and experiment results, it was found that the surface geometry of carbozole and azobenzene disperse red polymer was: this was physical adsorption between the carbazole group, which is from the monomer of carbazole and nitro-group which is from the monomer of azobenzene on the surface of rough silver film, and there is almost no interaction between the principal chain and the substrate because of the distance. This geometrical configuration of CAP on the surface of the substrate was proposed to damage the stabilities and efficiency of azobenzene derivatives based optical storage devices.

[Cooperative luminescence in Yb:YAG crystals].

Cooperative luminescence phenomenon of Yb:YAG crystals was studied. Up-converted blue luminescence was obviously observed in Yb:YAG under excitation in the near-infrared region with a wavelength 940 nm. Experimental evidence was provided by the fact that the intensity of 498 nm luminescence shows a quadratic dependence on excitation power, and the intensity of blue luminescence increased with the increase in Yb ion concentration. It is concluded that this luminescence is due to a cooperative process resulting from a strong interaction of Yb ions. The cooperative luminescence is possiblely assigned to the strong interaction of 4f(13) electrons and neighboring Yb3+ ions in a covalent host lattice such as YAG. Theoretical cooperative luminescence spectrum was calculated.

[Copper ion electrochemistry in treatment of bleeding and prolapse due to hemorrhoid, experimental and clinical studies].

OBJECTIVE: To observe the effect of copper ion electrochemistry (CIE) in treatment of bleeding and prolapse due to hemorrhoid. METHODS: Bleeding was caused at several points on the sacrospinal muscles of 26 rabbits. Routine hemostasis was used at one side (control side) and CIE was used on the opposite side (experimental side). The stanch times at the different sides were recorded. Then the rabbits were killed. Pathological examination was made to the lung, liver, and kidney to observe the amount of small thrombus and inflammation. CIE was performed at the right side of anus of 6 dogs and the right side was used as control side. Tissue specimens of rabbit muscle and dog anus mucosa were collected to examine the copper ion concentration. A copper needle was inserted into each pile to the depth of 10 - 15 mm for 4'40" (with the mean number of treated points of 9.8) upon 202 patients suffering from bleeding due to hemorrhoid, 79 with inner hemorrhoids and 123 patients with mixed hemorrhoids (experimental group). Another 171 patients suffering from bleeding due to hemorrhoid, 64 with inner hemorrhoids and 107 with mixed hemorrhoids were treated with suppository as controls. CEI was performed on 128 patients suffering from prolapse of hemorrhoid, 41 with inner hemorrhoids and 87 with mixed hemorrhoids (experimental group). Another 115 patients suffering from prolapse of hemorrhoid, 40 with inner hemorrhoids and 75 with mixed hemorrhoids were treated with suppository as controls. Biopsy specimens of anus mucosa were taken from 18 patients with mixed hemorrhoid who underwent CIE. The copper ion concentration was measured in 30 patients undergoing CIE. RESULTS: The stanch time in the experimental side of rabbit was (1.16 +/- 0.18) min, significantly shorter than that in the control side [(2.13 +/- 0.46) min, P = 0.0037]. Extensive small thrombi and edema of vascular wall were seen in the rabbit liver, lung, kidney, and muscle tissues in comparison with the tissues of the control side (P < 0.01). Copper ion complex was seen in the experimental rabbit tissues. The copper ion concentration was significantly higher in the experimental area of dog anus mucosa than in the control area. Clinical study showed that after CIE the curative rate for bleeding was 95.5%, significantly higher than that of the control group (8.8%, U = 44.6, P < 0.001). The curative rate for prolapse in the experimental group was 60.8%, significantly higher than that of the control group (20.9%, U = 313.2, P < 0.01). No patient felt pain while treated and later. After the CIE treatment, the patients only needed to take a rest for 4 hours. Pathology showed there were much more small thrombi in the treated tissues. The blood copper ion concentration in the trial group did not increase significantly after CIE in comparison with that before treatment. CONCLUSION: CIE is safe, effective and easy to perform in treatment of bleeding and prolapse due to hemorrhoid.