We demonstrate AC magnetic field sensing using spin coherence with the PDMR technique. AC magnetic field sensing using the PDMR technique is still challenging because the noise from a fluctuating magnetic environment is greater than the measured signal. We demonstrate AC magnetic field sensing with the PDMR technique by using a phase-cycling-based noise-canceling technique to suppress the noise. We observe electrically detected AC magnetic field sensing with a sensitivity of ~29 nT/√Hz. We will discuss the mechanism of PDMR of the NV centers and the sensitivity of AC magnetic field sensing with the electrical detection.
We demonstrate AC magnetic field sensing using spin coherence with the PDMR technique. AC magnetic field sensing using the PDMR technique is still challenging because the noise from a fluctuating magnetic environment is greater than the measured signal. We demonstrate AC magnetic field sensing with the PDMR technique by using a phase-cycling-based noise-canceling technique to suppress the noise. We observe electrically detected AC magnetic field sensing with a sensitivity of ~29 nT/√Hz. We will discuss the mechanism of PDMR of the NV centers and the sensitivity of AC magnetic field sensing with the electrical detection.
Electrical detection of nitrogen-vacancy (N-V) centers in diamond is advantageous for developing and integrating quantum information processing devices and quantum sensors and has the potential to achieve a higher collection efficiency than that of optical techniques. However, the mechanism for the electrical detection of N-V spins is not fully understood. In this study, we observe positive contrast in photocurrent detected magnetic resonance (PDMR). Note that negative PDMR contrast is usually observed. To discuss the sign of the PDMR contrast, we numerically analyze the dynamics of photocarrier generation by N-V centers using a seven-level rate model. It is found that the sign of the PDMR contrast depends on the difference in the photocurrent generated from the excited states and the metastable state of N-V centers. Furthermore, we demonstrate ac magnetic field sensing using spin coherence with the PDMR technique. ac magnetic field measurement with the PDMR technique is still challenging because the noise from a fluctuating magnetic environment is greater than the measured signal. Here, we introduce noise suppression using a phase-cycling-based noise-canceling technique. We demonstrate electrically detected ac magnetic field sensing with a sensitivity of 29 nT ${\mathrm{Hz}}^{\ensuremath{-}1/2}$. Finally, we discuss sensitivity enhancement based on the proposed model.
Electrical detection of a nitrogen-vacancy (NV) center in diamond is advantageous for developing and integrating quantum information processing devices and quantum sensors. However, the mechanism for the electrical detection of NV spins is not fully understood. In this study, we observe positive contrast in photoelectrically detected magnetic resonance (PDMR) despite the usually observed negative PDMR contrast. To discuss the sign of the PDMR contrast, we numerically analyze the dynamics of photocarrier generation by NV centers using a seven-level rate model. It is found that the sign of the PDMR contrast depends on the difference in the photocurrent generated from the excited states and the metastable state of NV centers. Furthermore, we demonstrate alternating-current (AC) magnetic field sensing using spin coherence with the PDMR technique using a phase-cycling-based noise-canceling technique to suppress the noise from a fluctuating magnetic environment. We obtained the sensitivity of AC magnetic-field of ${\sim}29{\text{nT}}/\sqrt {{\mathbf{Hz}}} $ with the PDMR technique.
Magnetometry by using NV center, a localized coherent spin consisting of a pair of nitrogen atom and atomic void, in diamond is now regarded as a promising technique due to its potential for high sensitivity and miniaturization. The primary application for NV magnetometry was realized by optically detected magnetic resonance (ODMR). There have been plenty of reports on demonstration of magnetic sensing by using ODMR1. Towards simpler and more reliable implementation of NV magnetometry, photocurrent-detected magnetic resonance2 (PDMR) is one of the key technologies to bypass the bulky confocal optics that are necessary for ODMR-based photoluminescence detection. In a PDMR scheme, meanwhile, we use photocurrent to read out the NV spin state, which necessitates laser irradiation only for photoexcitation and spin initialization. The key for high sensitivity of PDMR-based magnetometry3 is low noise to spin-dependent signal ratio. For this sake, it is essential to mitigate the unwanted spin-independent photocurrent while maximizing the PDMR signal. In this study, we employed two different laser power and time4 in the pulse sequence to improve the signal to noise ratio5. As a result, the magnetic sensitivity as high as 13 nT/Hz0.5 was achieved.
While photoelectric detection of magnetic resonance (PDMR) can be applied to miniaturize nitrogen-vacancy (NV) center-based quantum sensors, real demonstration of PDMR-based magnetic field sensing remains as a distinctive challenge. To tackle this challenge, in this article, we fabricate diamond samples with electrodes and microwave antenna on the surface, and realize PDMR by detecting photocurrent in picoampere range via various lock-in amplifying modes. We obtain a theoretical and experimental sensitivity 397 nT/Hz and 921 nT/Hz of magnetic field detection in DC-10 Hz range with a laser intensity and microwave frequency modulation mode, respectively, and demonstrate for the first time, a real-time tracking of alternating magnetic field with a standard deviation of 1.5 uT. Furthermore, we investigate systematically the dependence of the PDMR contrast, linewidth and the sensitivity on the laser and microwave power, and find a perfect agreement with a master equation-based theory. Thus, our results represent a critical step forward in transitioning PDMR from a spectroscopic technique to a practical sensing modality.
Nitrogen—Vacancy (NV) center in diamond can detect tiny magnetic field due to relative long coherence time even at room temperature. Its optical accessibility and capability of thin-film formation provide us an interesting sensing modality such as wide field imaging. We have reported phase sensitive protocol for ac magnetic field designed for wide field setup.[1] In this study we demonstrate an application of phase sensitive protocol; measuring distribution of ac magnetic field strength by phase sensing. Previous methods of multi-pulse quantum sensing such as XY8 realize quite high sensitivity of ac magnetic field. Since XY8 has dependencies on strength and phase of ac magnetic field, it is necessary to adjust ac phase to an optimal point in order to obtain a best sensitivity, and we cannot distinguish the effect of amplitude and phase. Recent studies have showed utilizing time-domain information is effective for improving frequency resolution of quantum sensing,[2,3] and we found same technique is also effective for simultaneous measurement of strength and phase. Here we propose a robust method for amplitude estimation by phase sensing. We added another signal for reference, then sensing phase difference between target signal and reference can be converted into amplitude. Conventional XY8 sensing is based upon fluorescence measurement which can be affected easily by many obstacles such as stray light, autofluorescence, and fringes of excitation laser. In the other hand, our method can be more robust because it is based on phase measurement. Nothing can change the phase except absorption of ac signal. This work was supported by MEXT Q-LEAP, CAO PRISM, Japan. [1] Mizuno et al., AIP advances 2018 [2][3] Boss, Schmitt
This paper aims to extend the understanding of the mechanism of photo-electrical detection of magnetic resonance (PDMR) in nitrogen-vacancy (NV) centres. This technique is particularly important for development of solid-state quantum computing platforms. In particular, we report on the new insight in the photocurrent (PC) generation and charge cycling in the single NV centre, which is related to PDMR contrast reaching 50\% and above. We develop a technique to locate PC related features. We find that electrons generated at the NV centre are stored in interface trap levels and establish that the interface states serve as an amplifier that can be driven by introducing a second laser into our confocal setup. We show that controlling these interface states allows one to significantly enhance the PDMR contrast. We develop a model that consistently explains observed amplification effects even without the application of a bias voltage.