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A quantum measurement method based on the quantum nature of antibunching photon emission has been developed to detect single particles without the restriction of the diffraction limit. By simultaneously counting the single-photon and two-photon signals with fluorescence microscopy, the images of nearby nitrogen-vacancy centers in diamond at a distance of 8.5±2.4 nm have been successfully reconstructed. Also their axes information was optically obtained. This quantum statistical imaging technique, with a simple experimental setup, can also be easily generalized in the measuring and distinguishing of other physical properties with any overlapping, which shows high potential in future image and study of coupled quantum systems for quantum information techniques. [ABSTRACT FROM AUTHOR]

The article presents a study which proposed a dynamic network with laser-controlled conducting filaments based on electric field-induced local insulator-metal transition of vanadium dioxide. Topics discussed include properties of vanadium dioxide film and imaging approach, controllable filament formation location by laser heating, and the synaptic cooperation and competition among the vanadium dioxide-based devices.

We demonstrate optical far-field super-resolution microscopy using an array of nitrogen vacancy centers in bulk diamond as near-field optical probes. The local optical field, which transmits through the nanostructures on the diamond surface, is measured by detecting the charge state conversion of the nitrogen vacancy center. Locating the nitrogen vacancy center with a spatial resolution of 6.1 nm is realized with charge state depletion nanoscopy. The nanostructures on the surface of a diamond are then imaged with a resolution below the optical diffraction limit. The results offer an approach to build a general-purpose optical super-resolution microscopy technique and a convenient platform for high spatial resolution quantum sensing with nitrogen vacancy centers. [ABSTRACT FROM AUTHOR]

The electron spin of the negatively charged the nitrogen vacancy center (NV-) in diamond can be optically polarized through intersystem crossing, which enables the defect to be used for quantum computation and metrology. In this work, we studied the electron spin depolarization effect of the NV center induced by charge state conversion, which was proven to be a spin-independent process. The spin-state initialization fidelity was largely affected by the charge state conversion process. As a result, the optical polarization of the electron spin decreased about 14%(31%) with a high-power continuous-wave (pulsed) green laser. Moreover, the undefined fluorescence anomalous saturation effect of the NV center was analyzed and explained in detail based on the spin depolarization. The results demonstrated that a weak laser should be used for initialization of the NV center. In addition, the power and polarization of a laser for NV spin detection should be carefully adjusted to obtain the highest fluorescence signal. Our work also provided information that can increase the understanding of the charge state conversion and spin polarization processes of the NV center for quantum information and sensing. [ABSTRACT FROM AUTHOR]

Single-crystal organic nanowires were fabricated with a soft-template-assisted self-assembly method in liquid phase. These nanowires with rectangular cross section can serve as resonators for exciton-photon coupling, leading to a microcavity effect and a relatively low threshold of laser actions. Two-photon-pumped blue lasing was observed in these organic waveguiding nanostructures above a threshold of 60 nJ, excited with a 750 nm near-infrared femtosecond pulse laser at 77 K. [ABSTRACT FROM AUTHOR]

Polarization dependence of the exciton-plasmon-photon conversion in silver nanowire-quantum dots structure was investigated using a scanning confocal microscope system. We found that the fluorescence enhancement of the CdSe nanocrystals was correlated with the angle between the excitation light polarization and the silver nanowire direction. The polarization of the emission was also related with the nanowire direction. It was in majority in the direction parallel with nanowire due to the nano-antenna effect. [ABSTRACT FROM AUTHOR]

Light has shown an incredible capability in precision measurement based on optomechanic interaction in high vacuum by isolating environment noises. However, there are still obstructions, such as displacement and mass estimation error, highly hampering the improvement of absolute accuracy at the nanoscale. Here, we present a nonlinearity based metrology to precisely measure the position and mass of a nanoparticle with optical levitation under 10-5 mbar. By precisely controlling the oscillation amplitude of the levitated nanoparticle at the nonlinear regime for high accuracy calibration, we realized a feasible sub-picometer-level position measurement with an uncertainty of 1.0% without the prior information of mass, which can be further applied to weigh the femtogram-level mass with an uncertainty of 2.2%. It will also pave the way to construct a fine-calibrated optomechanic platform in high vacuum for high sensitivity and accuracy measurement in force and acceleration at the nanoscale and the study in quantum superposition at the mesoscopic scale. [ABSTRACT FROM AUTHOR]

We investigate the enhanced electric dipole–dipole interaction of surface plasmon polaritons (SPPs) supported by a planar metal film waveguide. By taking two nitrogen-vacancy (NV) center electric dipoles in diamond as an example, both the coupling strength and collective relaxation of two dipoles are studied with the numerical Green Function method. Compared to two-dipole coupling on a planar surface, metal film provides stronger and tunable coupling coefficients. Enhancement of the interaction between coupled NV center dipoles could have applications in both quantum information and energy transfer investigation. Our investigation provides systematic results for experimental applications based on a dipole–dipole interaction mediated with SPPs on a planar metal film. [ABSTRACT FROM AUTHOR]

Single-photon flux is one of the crucial properties of nitrogen vacancy (NV) centers in diamond for its application in quantum information techniques. Here we fabricate diamond conical nanowires to enhance the single-photon count rate. Through the interaction between tightly confined optical mode in nanowires and NV centers, the single-photon lifetime is much shortened and the collection efficiency is enhanced. As a result, the detected single-photon rate can be at 564 kcps, and the total detection coefficient can be 0.8%, which is much higher than that in bulk diamond. Such a nanowire single-photon device with high photon flux can be applied to improve the fidelity of quantum computation and the precision of quantum sensors. [ABSTRACT FROM AUTHOR]

The coupled negatively charged nitrogen-vacancy (NV−) center system is a promising candidate for scalable quantum information techniques. In this work, ionized nitrogen molecules are implanted into bulk diamond to generate coupled NV− center pairs. The two-photon autocorrelation measurement and optically detected magnetic resonance measurement are carried out to confirm the production of the NV− center pair. Also, both 1.3 μs decoherence time and 4.9 kHz magnetic coupling strength of the NV− center pair are measured by controlling and detecting the spin states. Along with nanoscale manipulation and detection methods, such coupled NV− centers through short distance dipole-dipole interaction would show high potential in scalable quantum information processes. [ABSTRACT FROM AUTHOR]