Junko Ishi-Hayase1
Keio University1
Nitrogen-vacancy (NV) centers in diamond are promising as highly-sensitive nanoscale quantum sensors for measuring several kinds of physical quantities such as magnetic field, electric field, temperature, pressure, etc<sup>[1]</sup>. It is because that spin-triplet electronic ground states of NV centers can be coherently manipulated using microwave (MW) field and optically initialized/readout with long coherence time at room temperature. Optically detected magnetic resonance (ODMR) has been typically used to demonstrate quantum sensing using NV centers. In this study, we propose and demonstrate multiplexed sensor using NV center ensemble in diamond for simultaneously measuring AC magnetic field and temperature.<br/><br/>One of the proposed multiplexed sensors is based on double or triple electron spin resonance transitions induced by simultaneously applying MW and radio-frequency (RF) fields<sup>[2-6]</sup>. By utilizing eigenstates under bias magnetic field perpendicular to the NV axis, all transitions between spin-triplet states can be directly controlled by external MW and RF magnetic fields<sup>[4]</sup>. This is much different from the conventional quantum sensing under bias magnetic field parallel to the NV axis. In our method, we generate RF-dressed state or RF-doubly-dressed state by simultaneously irradiating continuous laser, MW and RF fields. The use of these dressed states enables us to implement MHz-range AC magnetic field sensing and temperature sensing using continuous-wave ODMR (CW-ODMR)<sup>[2,3,5,6]</sup>. the proposed method does not require a pulse sequence unlike conventional methods based on pulsed-ODMR; this greatly simplifies the procedure and apparatus needed for implementation. Moreover, the use of dressed states enables us to improve the sensitivity by suppressing the variances of strain and/or electric field<sup>[6]</sup>.<br/><br/>Another of the proposed multiplexed sensors is based on simultaneous manipulation of electronic spins of NV centers with different axes by using MW pulses with different frequencies<sup>[7,8]</sup>. The simultaneous spin manipulation enables us to improve the sensitivity by synthesizing the signals and suppressing the noise from NV centers with different axes. Here, we demonstrate vector magnetic field sensing and temperature sensing by applying the proposed multi-frequency manipulation technique to spin echo and Ramsey interference measurements in an ensemble of NV centers with random orientations. We find that the sensitivity using the multi-frequency manipulation is better than that using the conventional single-frequency manipulation.<br/><br/>Acknowledgement<br/>This work was done in collaboration with Dr. Matsuzaki, Dr. Watanabe (AIST), Prof. Mizuochi (Kyoto Univ.), Prof. Tokuda (Kanazawa Univ.), Prof. Kobayashi, Dr. Sasaki (Univ. Tokyo), Hayase Laboratory members (Keio Univ.). This work was supported by MEXT Q-LEAP (No. JPMXS0118067395), MEXT KAKENHI (No. 18H01502, 20H05661, 22H01558), and CSRN, Keio University. This work was supported by Leading Initiative for Excellent Young Researchers MEXT Japan and JST presto (Grant No. JPMJPR1919) Japan and Kanazawa University SAKIGAKE Project 2020. YM acknowledges support of Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan (20H05661).<br/><br/>Reference<br/>[1] L. Rondin, <i>et al.</i>, Rep. Prog. Phys. <b>77</b>, 056503 (2014).<br/>[2] S. Saijo, <i>et al</i>., Appl. Phys. Lett. <b>113</b>, 082405 (2018).<br/>[3] T. Yamaguchi, <i>et</i> <i>al</i>., Jpn. J. Appl. Phys. <b>58</b>, 100901 (2019).<br/>[4] T. Yamaguchi, <i>et al.</i>, Jpn. J. Appl. Phys. <b>59</b>, 110907 (2020).<br/>[5] K. J. Hallbäck, <i>et al.</i>, Proc. SPIE 117004A (2021).<br/>[6] H. Tabuchi, <i>et al.</i>, arXiv:2205.06976 (2022).<br/>[7] S. Kitazawa, <i>et al</i>., Phys. Rev. <b>A 96</b>, 042115 (2017).<br/>[8] K. Yahata, <i>et al</i>., Appl. Phys. Lett. <b>114</b>, 022404 (2019).