Optical Tweezers\nAssembled Nanodiamond Quantum Sensors

Here we show that gradient force optical tweezers can\nbe used to\nmediate the self-assembly of nanodiamonds into superstructures, which\ncan serve as optically trapped nanoscale quantum probes with superior\nmagnetic resonance sensing capabilities. Enhanced fluorescence rates\nfrom nitrogen-vacancy NV<sup>–</sup> defect centers enable\nrapid acquisition of optically detected magnetic resonance (ODMR),\nand shape-induced forces can improve both positioning accuracy and\norientation control. The use of confocal imaging can isolate the signal\nfrom individual nanodiamonds within the assembly, thereby retaining\nthe desirable properties of a single crystal probe. The improvements\nafforded by the use nanodiamond assemblies has the potential to resolve\ndynamic changes through, for example, real-time monitoring of the\nODMR contrast.