Markus Gregor | Searcharxiv

arXiv2024

Using low-cost Blu-Ray Optical Pickup Units for Measurement of Single Photon Emission from NV-Centers

This work presents a cost-effective method for collecting single photons emitted from single nitrogen-vacancy centers in nanodiamonds. Conventional components of a confocal laser-scanning microscope, such as microscope objectives and the piezo translation stages, are replaced by two affordable Blu-ray optical pickup units. A Hanbury Brown and Twiss setup is used to identify single photon emission. The proposed approach is inexpensive and simple and lowers the entry-level to single photon research for quantum technologies. This enables student lab experiments or demonstration experiments at schools and shows that efficient sources of quantum light can be made from standard components compatible with established industry processes.

quant-ph↗

arXiv2024

Microscale Fiber-Integrated Vector Magnetometer with On-Tip Field Biasing using NV Ensembles in Diamond Microcystals

In quantum sensing of magnetic fields, ensembles of nitrogen-vacancy centers in diamond offer high sensitivity, high bandwidth and outstanding spatial resolution while operating in harsh environments. Moreover, the orientation of defect centers along four crystal axes forms an intrinsic coordinate system, enabling vector magnetometry within a single diamond crystal. While most vector magnetometers rely on a known bias magnetic field for full recovery of three-dimensional field information, employing external 3D Helmholtz coils or permanent magnets results in bulky, laboratory-bound setups, impeding miniaturization of the device. Here, a novel approach is presented that utilizes a fiber-integrated microscale coil at the fiber tip to generate a localized uniaxial magnetic field. The same fiber-tip coil is used in parallel for spin control by combining DC and microwave signals in a bias tee. To implement vector magnetometry using a uniaxial bias field, we preselect the orientation of the diamond crystal and then fully characterize it by rotating a static magnetic field in three planes of rotation. We demonstrate the measurement of vector magnetic fields in the full solid angle with a shot-noise limited sensitivity of $19.4\:\textrm{nT/Hz}^{1/2}$ and microscale spatial resolution while achieving a cross section of the fiber sensor head below $1\:\textrm{mm}^2.$

physics.app-ph↗