December 19, 2016

Grid of nitrogen vacancies created in diamond using femtosecond lasers and grid can make quantum computers or magnetic sensors for imaging magnetic fields

Femtosecond laser writing of vacancies into diamond can be used to produce optically coherentNV−color centers at desired locations. The submicrometer positioning accuracy achieved is sufficient for placing NV−centers in optical structures such as multimode waveguides and whispering gallery resonators or under solid immersion lenses. The demonstrated accuracy is limited by the diffusion of the vacancies during annealing, and further improvements may be achieved using a higher nitrogen concentration in the starting material and an adjusted annealing recipe. In particular, high-precision depth positioning may be achieved by combining laser writing of vacancies with delta doping of a thin layer of nitrogen-rich material during growth. The adaptive optics used for aberration correction would also allow color centers to be positioned under microstructured surfaces. Beyond quantum photonic devices, the ability to write large and detailed 2D or 3D arrays of NV−defects may find application in magnetic field imaging systems. The laser writing technique demonstrated here for NV centers could be readily applied in conjunction with the writing of subsurface waveguides and electrodes, and can be adapted for the generation of other color centers and point defects in other wide bandgap materials.

Creating tiny grids of NV centers could be used for quantum computer and for tiny arrays of magnetic field sensors. The grid of magnetic field sensors could image magnetic fields

When nitrogen is surrounded by carbon it binds to three carbons but leaves the fourth carbon hanging.

The electron spends its time hanging around in the void between them, creating a kind of pseudo-atom with its own structure. The electron has spin states that can be manipulated with magnetic fields (these are used to store quantum states). These spin states are connected to energetic states that emit and absorb light.

Nature Photonics - Laser writing of coherent color centers in diamond

Optically active point defects in crystals have gained wide-spread attention as photonic systems that could be applied in quantum information technologies. 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 negatively charged nitrogen–vacancy (NV−) centers in diamond using laser writing.Aberration correction in the writing optics allows precise positioning of the vacancies within the diamond crystal, and subsequent annealing produces single NV−centers with a probability of success of up to 45 ± 15%, located within about 200 nm of the desired position in the transverse plane.Selected NV−centers display stable, coherent optical transitions at cryogenic temperatures, a prerequisite 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, and extend laser processing to the single-defect domain.

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