Abstract We developed a compact and portable measuring instrument using diamond NV centers that operates on the USB 3.0 power supply of a laptop computer. Its portability is achieved by the low power consumption of the optics, realized by the diamond corner cube that enhanced the current of the photodiode to 2.1 times higher than that of the planar diamond, and that of the microwave source, reduced by 20 dB, which was realized by a microwave resonator using a λ/4 open stub that strongly magnetically drives the NV center. These results contribute to the social implementation of diamond sensors.
Abstract We developed a compact and portable measuring instrument using diamond NV centers that operates on the USB 3.0 power supply of a laptop computer. Its portability is achieved by the low power consumption of the optics, realized by the diamond corner cube that enhanced the current of the photodiode to 2.1 times higher than that of the planar diamond, and that of the microwave source, reduced by 20 dB, which was realized by a microwave resonator using a λ/4 open stub that strongly magnetically drives the NV center. These results contribute to the social implementation of diamond sensors.
Abstract We developed a compact, portable quantum sensor module for pulsed measurements using diamond nitrogen-vacancy (NV) centers, an excitation laser diode of 3 mW and a microwave source of 15 dBm. This module allowed the evaluation of ensemble diamond NV centers for measuring magnetic fields by continuous wave— optically detected magnetic resonance (ODMR), Rabi oscillation, pulsed ODMR, Ramsey measurement and spin-echo measurement. The sensitivity through pulsed measurements reached 40 nT/ Hz at 1 Hz, which achieved higher sensitivity by one order, especially at a frequency around 1 Hz compared with previously reported compact modules using diamond NV centers.
Nitrogen-vacancy (NV) color centers in diamond are promising solid-state quantum sensors working at room temperature. The number of NV centers limits the magnetic sensitivity of the quantum magnetometer. Increasing the number of NV centers is a challenging task due to technical issues such as microwave power density, detection noise.Here, we developed the sensor system with a large detection volume which contains a lot of NV centers. The microwave circuit enhances microwave power density. Digital filter with frequency modulation of microwave allows us to detect the magnetic field with low noise. Consequently, we obtained a DC magnetic field sensitivity of 980 pT/√Hz.This work was supported by MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118067395.
The nitrogen-vacancy (NV) color center in diamond has found applications in magnetometry across various geometrical scales. In particular, vector magnetometry using hand-held devices with low power consumption is of interest for mobile and geological applications. However, such a device requires efficient driving of the four different orientations of the NV center, thus placing demands on a broadband microwave resonator that provides a uniform and highly insensitive microwave magnetic field at the resonance frequencies of the NV centers. Here, we propose a unique planar resonator design that enables efficient driving of all four orientations of NV color centers over a 100 MHz range with only 0.5 W of microwave input power and 250 mW of laser power, allowing vector magnetic field measurements. Using the planar resonator to drive NV centers in diamond, a compact vector magnetometer was fabricated and experimentally studied. The sensitivity of the device is about 1.2 nT/Hz. While this is not a record sensitivity for diamond-based magnetometers, this device occupies its own niche as a compact hand-held magnetometer.
The physical properties of diamond crystals, such as color or electrical conductivity, can be controlled via impurities.In particular, when doped with nitrogen and under certain conditions, optically active nitrogen-vacany centers (NV) can be induced.The center is an outstanding quantum spin system that enables, under ambient conditions, optical initialization, readout, and coherent microwave control with applications in sensing and quantum information.Under optical and radio frequency excitation, the Zeeman splitting of the degenerate states allows the quantitative measurement of external magnetic fields with high sensitivity.This study provides a pedagogical introduction to the properties of the NV centers as well as a step-by-step process to develop and test, a simple magnetic quantum sensor based on color centers with large potential for the development of highly compact multi-sensor systems.
This thesis investigates the theoretical foundations, material properties, and experimental realization of quantum sensors based on the Nitrogen-Vacancy (NV) centers in diamond, a solid-state system that combines quantum coherence with room-temperature operability. The first chapter introduces the principles of quantum sensing, outlining the fundamental definitions, operating protocols, and physical processes underlying the quantum measurement paradigm. Emphasis is placed on the quantum sensing Hamiltonian and the distinction between various classes of quantum sensors. The second chapter focuses on diamond as a host material and on the NV center as a quantum defect. The electronic structure, optical transitions, and spin properties of the NV center are analyzed in detail. Several techniques of NV-based magnetometry are presented, including continuouswave and pulsed optically detected magnetic resonance (ODMR). The discussion also addresses coherence times (T1, T2, and T∗2 ) and methods of diamond synthesis together with NV-center generation through irradiation and annealing. Chapter three develops the physical theory describing the NV center. The Hamiltonian formalism includes spin-spin, hyperfine, and quadrupolar interactions, as well as couplings to external magnetic fields. The chapter further introduces the Bloch sphere representation, magnetic resonance phenomena, and models of lightmatter interaction, ranging from the semiclassical to the fully quantum Rabi framework. A seven-level rate-equation model is proposed to capture the spin dynamics and optical cycling processes of the NV center. The fourth chapter reports the experimental results. After describing materials and methods, several ODMR-based vector magnetometry experiments are presented, highlighting different spectral regimes and the dependence of resonance features on the external magnetic field geometry. Additional studies demonstrate temperature sensing and microwave-free magnetometry techniques for mapping magnetic field distributions. Sensitivity analysis and calibration procedures are also discussed.
This dissertation presents the development and characterization of fully integrated quantum sensors based on nitrogen vacancy (NV) centers in diamond. While existing NV-based sensors are typically large and complex, this work focuses on miniaturizing the technology and demonstrating its application as a current sensor. The primary research question addressed is whether fully integrated NVbased quantum sensors with LED excitation can be realized with performance comparable to conventional sensor technologies. To this end, two sensor prototypes were developed: one as the smallest fully integrated NV quantum sensor with a complete electrical interface to date, achieving a sensitivity of 32 nT/ √ Hz; and another as the first NV-based sensor implemented on a flexible PCB, which is even smaller and achieves a sensitivity of 96 nT/ √ Hz. Thereby both sensors utilize randomly oriented diamond microcrystals. Methodologically, a novel procedure for determining the orientation of the diamond crystals was developed, allowing for effective signal extraction despite the random crystal orientation. Further, magnetic fields were simulated using COMSOL Multiphysics to investigate the feasibility of applying these sensors for current measurements. In this context, a new measurement concept for determining currents in segmented multi-wire cables of three-phase power grids was developed, demonstrating the potential of NV-based sensors in smart grid applications. The results indicate that these quantum sensors can be more easily integrated, even when diamonds are placed arbitrarily, thus paving the way for new applications in smart grid monitoring and other fields requiring compact, high-precision magnetic field sensors.