Photonic-integrated quantum sensor array for microscale magnetic localisation

This paper demonstrates a photonic-integrated quantum sensor array for high-precision magnetic localisation at the microscale. The authors integrate nitrogen-vacancy (NV) centers in diamond with foundry silicon-nitride photonic circuits, enabling the scalable operation of eight NV sensors. The setup allows simultaneous and independent readout from each sensor, achieving high spatial resolution.

Key points from the study include:

1. NV Sensors for Magnetic Localisation: The platform employs eight NV sensors, each integrated with photonic waveguides for enhanced sensitivity and low crosstalk. The sensors use continuous-wave optically-detected magnetic resonance (CW-ODMR) measurements to detect magnetic fields at the nanoscale.

2. Magnetic Field Reconstruction: Using machine learning techniques, the team reconstructed the position of a 30 µm-sized magnetised needle tip, achieving localisation with an error below the size of the needle. This method allows tracking of dynamic movement, offering real-time magnetic localisation for small-scale objects.

3. Tracking and Sensitivity: The platform can track moving magnetic objects with high fidelity by adjusting integration time and frame rates. The authors show that shorter integration times yield noisier results, while higher frame rates are suitable for faster-moving objects, albeit with increased noise. They also demonstrate the system's application for tracking magnetic microrobots, which can be used in biological and clinical scenarios, such as drug delivery.

4. Simulation of Microrobot Tracking: The study also includes simulations showing the platform’s potential for tracking both the position and orientation of magnetic microrobots in real-life conditions, such as navigating optically-inaccessible environments. The results suggest that the system can precisely monitor both position (with an error of 10 µm) and orientation (with an error of 5°).

5. Application in Biomedical and Clinical Fields: This work points to the potential of NV-based photonic quantum sensing platforms for real-world applications, such as biosensing and monitoring dynamic objects in clinical settings, without the need for complex bulk optics or direct optical access.

This research represents a significant step toward practical, scalable quantum sensing systems for use in real-world environments, especially in biological, medical, and engineering fields.