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.
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.
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.
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.
Abstract The photoelectric detection of nitrogen‐vacancy (NV) magnetic resonance (PDMR) in diamond, used for spin state detection and based on reading the photocurrent resulting from NV ionization, offers physical and technical advantages for the development of miniaturized and scalable quantum sensors, as well as solid‐state quantum information devices integrated with electronics. Charge exchanges between NV centers and other optoelectrically active defects in diamond are an essential part of the PDMR scheme, impacting the spin‐state control and the performances of the photoelectric readout. Through experimental characterization and modeling, processes governing the spin‐state contrast, in particular the hole carrier contribution to the photocurrent and the role of acceptor‐type defects are discussed. Such acceptor defects can act as traps for free electrons resulting from NV photoionization. Consequently, the hole current can increase at resonance, ultimately leading to an inversion of the sign of PDMR resonances, i.e. to a positive spin contrast. Based on these findings, a method to improve PDMR performances in terms of spin contrast and photoelectric detection rate by selectively ionizing low‐energy acceptor defects using a bias red illumination is proposed. This method is shown to lead to a significant improvement of the photoelectric spin detection sensitivity, important for future practical devices.
The core issue for the implementation of NV center qubit technology is a sensitive readout of the NV spin state. We present here a detailed theoretical and experimental study of NV center photoionization processes, used as a basis for the design of a dual-beam photoelectric method for the detection of NV magnetic resonances (PDMR). This scheme, based on NV one-photon ionization, is significantly more efficient than the previously reported single-beam excitation scheme. We demonstrate this technique on small ensembles of $\ensuremath{\sim}10$ shallow NVs implanted in electronic grade diamond (a relevant material for quantum technology), on which we achieve a cw magnetic resonance contrast of 9%---three times enhanced compared to previous work. The dual-beam PDMR scheme allows independent control of the photoionization rate and spin magnetic resonance contrast. Under a similar excitation, we obtain a significantly higher photocurrent, and thus an improved signal-to-noise ratio, compared to single-beam PDMR. Finally, this scheme is predicted to enhance magnetic resonance contrast in the case of samples with a high proportion of substitutional nitrogen defects, and could therefore enable the photoelectric readout of single NV spins.
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.
Abstract A novel method for reading out the electron spin state of the negatively charged nitrogen‐vacancy (NV) point defect in diamond, based on photoelectric detection of NV magnetic resonances (PDMR), is reviewed. As a convenient way to measure the spin state of qubits, the presented technique is anticipated to lead to a vast range of applications in the field of quantum technologies. It has been demonstrated that this method can be used both in continuous‐wave mode and for the pulse readout of coherently manipulated NV− spins. The PDMR technique presents interesting advantages over the commonly used optical detection of magnetic resonances (ODMR) and was recently downscaled to the reading out of a single NV− spin qubit. The principles, current developments, advantages, and drawbacks of PDMR are presented in this progress report. A complete to‐date methodology of NV photoelectric readout is described and PDMR is compared to ODMR. Future developments and possible improvements of the technique are mentioned. The results of the latest studies, aiming at overcoming limitations in the PDMR contrast through a better understanding of NV photo‐physics and of charge exchanges between NV centers and other electrically active defects, are discussed.