Laser writing of individual atomic defects in a crystal with near-unity yield

Atomic defects in wide band gap materials show great promise for development of a new generation of quantum information technologies, but have been hampered by the inability to produce and engineer the defects in a controlled way. The nitrogen-vacancy (NV) color center in diamond is one of the foremost candidates, with single defects allowing optical addressing of electron spin and nuclear spin degrees of freedom with potential for applications in advanced sensing and computing. Here we demonstrate a method for the deterministic writing of individual NV centers at selected locations with high positioning accuracy using laser processing with online fluorescence feedback. This method provides a new tool for the fabrication of engineered materials and devices for quantum technologies and offers insight into the diffusion dynamics of point defects in solids.Comment: 16 pages, 8 figure

Microcavity enhanced single photon emission from two-dimensional WSe2

Atomically flat semiconducting materials such as monolayer WSe2 hold great promise for novel optoelectronic devices. Recently, quantum light emission has been observed from bound excitons in exfoliated WSe2. As part of developing optoelectronic devices, the control of the radiative properties of such emitters is an important step. Here, we report the coupling of a bound exciton in WSe2 to open microcavities. We use a range of radii of curvature in the plano-concave cavity geometry with mode volumes in the λ3 regime, giving Purcell factors of up to 8 while increasing the photon flux five-fold. Additionally, we determine the quantum efficiency of the single photon emitter to be η=0.46±0.03. Our findings pave the way to cavity-enhanced monolayer based single photon sources for a wide range of applications in nanophotonics and quantum information technologies

Laser writing of coherent colour centres in diamond

Optically active point defects in crystals have gained widespread attention as photonic systems that can find use in quantum information technologies [1,2]. However challenges remain in the placing of individual defects at desired locations, an essential element of device fabrication. Here we report the controlled generation of single nitrogen-vacancy (NV) centres in diamond using laser writing [3]. The use of aberration correction in the writing optics allows precise positioning of vacancies within the diamond crystal, and subsequent annealing produces single NV centres with up to 45% success probability, within about 200 nm of the desired position. Selected NV centres fabricated by this method display stable, coherent optical transitions at cryogenic temperatures, a pre-requisite for the creation of distributed quantum networks of solid-state qubits. The results illustrate the potential of laser writing as a new tool for defect engineering in quantum technologies

Towards an efficient spin-photon interface based on cavity-coupled NV centres in diamond membranes

Quantum computation and information processing is an exciting multi-disciplinary field, whose objective is to harness the power of superposition and entanglement of quantum states to establish a new regime of computation for Mankind. This work demonstrates our efforts, in both materials and device engineering, towards building an efficient spin-photon interface for a promising solid-state spin qubit, namely the nitrogen-vacancy (NV) centre in diamond. Improvement in optical coherence of NV centre is realised via the novel laser-writing fabrication technique and quantified using high-resolution spectroscopy. A new metric concerning the charge-state stability of the NV centre is introduced to better translate the measured NV quality to entanglement generation efficiency. To address the low branching ratio of NV emission into the zero-phonon line (ZPL) transition, a hybrid open-cavity device incorporating low-dimensional micro-structured NV-containing diamond membrane is fabricated and characterised. In addition to the more commonly quoted emission enhancement factor, the collection efficiency of the cavity device is also quantified via numerical simulations. Combining all observed improvements in key metrics under the framework of double-heralding entanglement schemes, a two order of magnitude increase in entanglement generate rate can be expected. The established simulation methodology is widely applicable in the design and analysis of similar devices with an emitter-in-cavity setup

Laser writing of individual nitrogen-vacancy defects in diamond with near-unity yield

Atomic defects in wide-bandgap materials, such as the nitrogen-vacancy (NV) color center in diamond, show considerable promise for the development of a new generation of quantum information technologies, but progress has been hampered by the inability to produce and engineer the defects in a controlled manner. Here, we demonstrate an all-optical method for the deterministic writing of individual NV centers at selected locations with high positioning accuracy. Ultrashort pulse laser processing is used to both create and diffuse defects inside the crystal through local annealing. During the laser-annealing process, online fluorescence feedback provides a trigger to stop processing once the NV formation is detected. This method provides a new tool for the optical fabrication of engineered materials and devices for quantum technologies

Normal Values for CD4 and CD8 Lymphocyte Subsets in Healthy Chinese Adults from Shanghai

The aim of this study was to establish reference ranges for lymphocyte subsets in Chinese adults. Venous blood specimens were obtained from 614 healthy, human immunodeficiency virus (HIV)-seronegative adults in Shanghai. Flow cytometry was used to determine percentages and absolute numbers of CD4 and CD8 T lymphocytes. Mean values for CD4 and CD8 lymphocytes were 727 and 540 cells/μl, respectively, yielding a CD4/CD8 ratio of 1.49. While CD8 lymphocyte values varied with age and gender, no significant differences in CD4 lymphocyte values were observed. Shanghai adults had approximately 100 fewer CD4 lymphocytes/μl on average than Caucasians, suggesting that lower CD4 lymphocyte cutoffs for classifying and monitoring HIV infection may be needed in China

Tunable cavity coupling of the zero phonon line of a nitrogen-vacancy defect in diamond

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Dataset: Laser writing of individual nitrogen-vacancy defects in diamond with near-unity yield

This archive contains the underlying data used in the preparation of the manuscript: YC Chen et al, "Laser writing of individual nitrogen-vacancy defects in diamond with near-unity yield" Optica 6 (5), 662-667 (2019). There is photoluminessence data from a confocal microscope taken to analyse the orientation, positioning accuracy and number of nitrogen vacancy defects written in three different arrays inside diamond. There is also included the photoluminessence feedback signal recorded when laser writing each of the defects. Matlab and Origin are required to open some of the files

3896001.pdf

Supplementary Informatio