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Applied Physics Letters

Microwave-photonic control of optically accessible spin defects in diamond

Mohammad Reefaz Rahman, Ryan C Goldsmith, Karsten Schnier, Benjamin J. Lawrie, Jason D. McKinney, Joseph M. Lukens, Seongsin M. Kim, Patrick Kung

Published Aug 3, 2026• 1 citation
Publisher

Abstract

A growing variety of optically accessible spin qubits have emerged in recent years as key components for quantum sensors, computers, and memories. However, the scalability of conventional spin-based quantum architectures remains limited by direct microwave delivery, which introduces thermal noise, electromagnetic crosstalk, and design constraints for cryogenic, high-field, and distributed systems. In this work, we present a unified framework for RF-over-fiber (RFoF) control of spins accessible through optically detected magnetic resonance (ODMR) spectroscopy of nitrogen-vacancy (NV) centers in diamond. The RFoF platform relies on an intensity-modulated 1310 nm laser carrying microwave signals over fiber and a high-speed photodiode for optical-to-electrical conversion to drive NV spin transitions. We report an RFoF power-conversion efficiency of 3.42% for an RF output PRF,out=−5.5 dBm at 2.87 GHz, enabling clear resolution of Zeeman splitting in proportion to an applied magnetic field. The RFoF architecture provides a path toward low-noise, thermally isolated, and cryo-compatible ODMR systems at sub-THz frequencies, thus bridging conventional spin-based quantum sensing protocols with emerging distributed quantum technologies.

DOI
10.1063/5.0336858

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A growing variety of optically accessible spin qubits have emerged in recent years as key components for quantum sensors, computers, and memories. However, the scalability of conventional spin-based quantum architectures remains limited by direct microwave delivery, which introduces thermal noise, electromagnetic crosstalk, and design constraints for cryogenic, high-field, and distributed systems. In this work, we present a unified framework for RF-over-fiber (RFoF) control of spins accessible through optically detected magnetic resonance (ODMR) spectroscopy of nitrogen-vacancy (NV) centers in diamond. The RFoF platform relies on an intensity-modulated 1310 nm laser carrying microwave signals over fiber and a high-speed photodiode for optical-to-electrical conversion to drive NV spin transitions. We report an RFoF power-conversion efficiency of 3.42% for an RF output PRF,out=−5.5 dBm at 2.87 GHz, enabling clear resolution of Zeeman splitting in proportion to an applied magnetic field. The RFoF architecture provides a path toward low-noise, thermally isolated, and cryo-compatible ODMR systems at sub-THz frequencies, thus bridging conventional spin-based quantum sensing protocols with emerging distributed quantum technologies.
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We present an RF-over-fiber (RFoF)-centered experimental platform for optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in diamond, motivated by the need for remote, electrically isolated, and cryo-compatible microwave delivery in future quantum sensing systems. Conventional coax-fed ODMR measurements are first used to establish the baseline dependence of resonance contrast and linewidth on microwave power, as well as the magnetic-field- and angle-dependent spectral response of the NV ensemble. In the baseline configuration, the ODMR contrast exceeds 11% at 25 dBm microwave drive, while magnetic-field and orientation sweeps confirm the expected Zeeman splitting and field-projection dependence of the ensemble response. These reference measurements are then used to benchmark a 1310 nm intensity-modulated RFoF link in which the microwave drive is transported over optical fiber and recovered at the sensing node using a high-speed photodiode. Under remote photonic delivery, the recovered signal reproduces the characteristic Zeeman-split ODMR response of the NV ensemble over the low-field regime studied. At a recovered RF power of −5.5 dBm, the RFoF-driven ODMR contrast remains in the 0.6–0.9% range, while at a higher-power operating point of −0.7 dBm the contrast increases to greater than 2.2%. The corresponding overall power-conversion efficiencies are 3.42% and 2.52%, respectively. These results establish that photonic microwave transport can preserve physically meaningful NV ODMR signatures while providing a practical route toward remote microwave delivery, reduced electromagnetic interference, and future thermally constrained or cryogenic spin-control architectures.
Nitrogen-vacancy (NV) centers in diamond are a leading platform for solid-state quantum sensing and quantum information processing. While most optical studies rely on the visible fluorescence associated with the triplet transitions, the infrared singlet transition near 104210421042 nm, which is typically considered dark within the singlet manifold of the NV optical cycle, provides an alternative optical channel. Here, we report wavelength-resolved optically detected magnetic resonance (ODMR) measurements of this infrared emission. We directly observe ODMR contrast in the 104210421042 nm emission and analyze its dependence on the magnetic field. The field-dependent spectral dispersion of the ODMR signal demonstrates that the spin-state information encoded in the NV center is transcribed to the infrared singlet emission through the spin-selective intersystem crossing, in close analogy to the visible fluorescence readout. These results establish infrared ODMR as a high-fidelity optical readout pathway. Crucially, by extending spin-state transcription directly into the 1300−16001300-16001300−1600 nm range, this work demonstrates a direct, conversion-free interface between diamond spin-qubits and standard telecommunication infrastructure, bypassing the efficiency bottlenecks of active frequency conversion and benefiting from the already well-developed technologies in this range of the electromagnetic spectrum.
The nitrogen-vacancy (NV) center in diamond is a leading solid-state platform for room-temperature quantum magnetometry owing to its long spin coherence times, optical spin initialization and readout, and high sensitivity to magnetic, electric, and thermal perturbations. As NV-based optically detected magnetic resonance (ODMR) systems transition from controlled laboratory environments toward portable and field-deployable sensors, a detailed understanding of realistic noise sources and experimental imperfections becomes essential for optimizing performance and sensitivity. In this work, we present a comprehensive simulation framework, i.e., a digital twin, for continuous-wave wide-field ODMR in NV-center ensembles. The model is built upon a physically consistent seven-level description of the NV center and incorporates a broad range of experimentally relevant noise and imperfection mechanisms as modular, parameterized components. These include laser and microwave amplitude fluctuations, microwave phase noise, uncertainty in the NV gyromagnetic ratio, spin dephasing, temperature-induced shifts of the ground-state zero-field splitting, surface-induced magnetic field perturbations, and photon shot noise. Power broadening and contrast degradation arising from optical and microwave driving are captured self-consistently through linewidth calculations. Also, the spatial inhomogeneity is modeled via a Gaussian laser intensity profile across the sensing region...
The Nitrogen-Vacancy (NV) center in diamond is a prominent quantum system leveraged for advanced quantum metrology, particularly in high-precision magnetometry and high-resolution quantum imaging, exploiting the Optically Detected Magnetic Resonance (ODMR) spectroscopy technique. Proper radio-frequency (RF) excitation of NV centers is critical in order to manipulate these quantum states effectively. Our research focuses on optimizing the continuous-wave RF excitation of ensembles of NV centers on coplanar waveguide transmission lines (CPW-TL), measuring the centers' photoluminescence (PL) signal as a function of RF power. This setup enhances the sensitivity and resolution of the NV center PL signal. By combining CPW-TL lines with nanodiamonds, our approach aims to develop a scalable and tunable platform that can be deployed in a variety of quantum sensing scenarios, including in biomedical applications, navigation systems, environmental monitorlng, and beyond.
Nitrogen-vacancy (NV) centers in diamond are solid-state quantum sensors that operate at room temperature and allow optical readout of spin states through optically detected magnetic resonance (ODMR). Reliable ODMR measurements need controlled microwave excitation to manipulate NV spin states and modulate their fluorescence. In this paper, we report on ensemble NV centers’ interaction with microwave fields transmitted by printed-circuit-board (PCB) radio-frequency (RF) devices. Two microwave structures, a coplanar waveguide transmission line (CPW-TL) and a single-finger interdigitated capacitor (IDC), are designed and impedance-matched at the NV zero-field splitting frequency. Nanodiamond solutions containing NV ensembles are deposited as few-microliter droplets onto the PCB devices and dried, forming localized NV layers on the RF structures. Two-dimensional fluorescence scans are used to link spatial changes in NV fluorescence to the microwave field distributions created by each device geometry. CPW-TLs enable interaction over extended regions along the transmission line, while IDCs produce localized excitation near the capacitive gaps.