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arXiv:2602.20437

Toward a CMOS-integrated quantum diamond biosensor based on NV centers

Ioannis Varveris, Gianni D. Aliberti, Felix J. Barzilaij, Zhi Jin, Samantha A. van Rijs, Qiangrui Dong, Daan Brinks, Salahuddin Nur, Ryoichi Ishihara

physics.app-phquant-phSubmitted Feb 24, 2026• Announced Feb 25, 2026
arXivHTMLPDF

Abstract

We report progress toward a CMOS-integrated quantum diamond biosensing platform that combines nitrogen-vacancy (NV) centers in diamond with a custom 40 nm CMOS Single-Photon Avalanche Diode (SPAD) array. The system integrates on-chip active quenching and digital readout with external FPGA-based photon counting, compact microwave delivery, and practical optical excitation and collection schemes to support widefield optically detected magnetic resonance (ODMR). System-level design considerations spanning fluorescence collection efficiency, detector count-rate capability, and microwave homogeneity are analyzed with biological compatibility and scalability in mind. Using superparamagnetic iron oxide nanoparticle (SPION)-labeled HEK293T cells as a representative use case, simple dipole-field estimates indicate that sub-$μ$T sensitivity is required to resolve ODMR shifts within typical ensemble linewidths. Based on the proposed architecture and efficiency analysis, a magnetic field sensitivity of approximately 90 nT/$\sqrt{\mathrm{Hz}}$ per pixel is estimated. These results outline a practical path from optics-heavy quantum diamond microscopes toward compact, CMOS-integrated NV-based biosensors for quantitative magnetic imaging in complex biological environments.

Comments
19 pages, 20 figures

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We report progress toward a CMOS-integrated quantum diamond biosensing platform that combines nitrogen-vacancy (NV) centers in diamond with a custom 40 nm CMOS Single-Photon Avalanche Diode (SPAD) array. The system integrates on-chip active quenching and digital readout with external FPGA-based photon counting, compact microwave delivery, and practical optical excitation and collection schemes to support widefield optically detected magnetic resonance (ODMR). System-level design considerations spanning fluorescence collection efficiency, detector count-rate capability, and microwave homogeneity are analyzed with biological compatibility and scalability in mind. Using superparamagnetic iron oxide nanoparticle (SPION)-labeled HEK293T cells as a representative use case, simple dipole-field estimates indicate that sub-μμμT sensitivity is required to resolve ODMR shifts within typical ensemble linewidths. Based on the proposed architecture and efficiency analysis, a magnetic field sensitivity of approximately 90 nT/Hz\sqrt{\mathrm{Hz}}Hz​ per pixel is estimated. These results outline a practical path from optics-heavy quantum diamond microscopes toward compact, CMOS-integrated NV-based biosensors for quantitative magnetic imaging in complex biological environments.
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AbstractNitrogen-vacancy (NV) centers in diamond show disruptive potential in quantum sensing, enabling groundbreaking applications in nanoscale microscopy [1] and single-cell imaging [2]. They also promise insight into processes in complex electrochemical systems such as batteries [3]. However, most successes in these applications remain bound to laboratory conditions.We present a novel architecture for an endoscopic and fully fiber-coupled quantum magnetometer. Our sensor features a 5 mm diameter head with a micro-lens optical front-end for efficient optical excitation and fluorescence collection. An FPGA integrates the control and readout functionalities, including microwave synthesis and lock-in demodulation. This highly integrated platform achieves a magnetic field sensitivity of 150 pT/√Hz, presenting a performance record for endoscopic CW-ODMR based NV-based sensors. We verify the sensor's practical utility by performing 2D magnetic field scans of a commercial battery, demonstrating its capability in a real application scenario. This work marks a significant advance in the transition of endoscopic quantum sensors from the lab to the field.
We present key building blocks for an integrated approach to NV-diamond magnetometry.The work combines application-specific integrated circuits (ASICs) for control and data processing with integrated optical waveguides within a compact architecture.The objective is to investigate miniaturized and scalable implementation strategies for diamond-based NV magnetic field sensors while maintaining suitable optical excitation conditions and compatibility with optical readout.Within a photonic integrated circuit (PIC), both the excitation path and the signal and reference paths were realized on a single chip.Two different photonic chip architecture concepts were implemented and characterized with respect to optical throughput and assembly complexity.Experimental results show that integrated Si3N4 waveguides, in combination with additively manufactured micro-optics, can provide efficient diamond excitation with power densities exceeding 1 kW/cm².In addition, preliminary feasibility experiments indicate that the presented approach is compatible with optically detected magnetic resonance (ODMR) measurements.The presented results provide a basis for future integrated NV-based sensing systems.
On-chip magnetic field sensing with nitrogen-vacancy (NV) centers in diamond requires scalable integration of 3D waveguides into diamond substrates. Here, we develop a sensing array device with an ensemble of shallow implanted NV centers integrated with arrays of laser-written waveguides for excitation and readout of NV signals. Our approach enables an easy-to-operate on-chip magnetometer with a pixel size proportional to the Gaussian mode area of each waveguide. The performed continuous wave optically detected magnetic resonance on each waveguide gives an average dc-sensitivity value of (195±3) nT/Hz, which can be improved with lock-in-detection or pulsed-microwave sequences. We apply a magnetic field to separate the four NV crystallographic orientations of the magnetic resonance and then utilize a DC current through a straight wire antenna close to the waveguide to prove the sensor capabilities of our device. We reconstruct the complete vector magnetic field in the NV crystal frame using three different NV crystallographic orientations. By knowing the polarization axis of the waveguide mode, we project the magnetic field vector into the lab frame.
A simple and convenient design enables real-time three-dimensional position tracking of nitrogen-vacancy (NV) centers in diamond. The system consists entirely of commercially available components (a single-photon counter, a high-speed digital-to-analog converter, a phase-sensitive detector-based feedback device, and a piezo stage), eliminating the need for custom programming or rigorous optimization processes. With a large input range of counters and trackers combined with high sensitivity of single-photon counting, high-speed position tracking (upper bound recovery time of 0.9 s upon 250 nm of step-like positional shift) not only of bright ensembles, but also of low-photon-collection-efficiency single to few NV centers (down to 103 s−1) is possible. The tracking requires position modulation of only 10 nm, which allows simultaneous position tracking and pulsed measurements in the long term. Therefore, this tracking system enables measuring a single-spin magnetic resonance and Rabi oscillations at a very high resolution even without photon collection optimization. The system is widely applicable to various fields related to NV center quantum manipulation research such as NV optical trapping, NV tracking in fluid dynamics, and biological sensing using NV centers inside a biological cell.