Highly localized delivery of microwaves to quantum bits with a scanning loop micro-antenna

We demonstrate highly localized delivery of microwaves to quantum bits with a scanning loop micro-antenna. The quantum state of the qubits (ensembles of nitrogen vacancy centers in diamond) is read out optically, via Optically Detected Magnetic Resonance (ODMR). A 600 × 600 μm2 via-based PCB loop antenna is used as the excitation source. A Sensapex piezo micromanipulator provides precise control of the antenna position above diamond samples containing nitrogen-vacancy (NV) centers, enabling spatially resolved ODMR measurements. Line- and two-dimensional imaging scans reveal the local microwave near-field distribution generated by the loop antenna. These results demonstrate spatially resolved ODMR mapping using a compact free-space optical configuration and establish a basis for future NV-based quantum sensing and microwave field characterization, as well as laying the foundation for quantum state manipulation of individual qubits using programmable, highly localized delivery of microwaves.