@article{oai:repo.qst.go.jp:00079933,
 author = {Hayashi, Kan and Matsuzaki, Yuichiro and Ashida, Takaki and Onoda, Shinobu and Ohshima, Takeshi and Hatano, Mutsuko and Taniguchi, Takashi and Morishita, Hiroki and Fujiwara, Masanori and Mizuochi, Norikazu and Onoda, Shinobu and Ohshima, Takeshi},
 issue = {5},
 journal = {Journal of the Physical Society of Japan},
 month = {Apr},
 note = {NV centers in diamond have been considered as an important building block for the realization of quantum information processing such as quantum simulation, quantum memory, and quantum metrology. To maximize the potential of the NV centers, it is essential to understand the mechanism of the decoherence. Existing theories predicted a relationship between the coherence time and spin concentration (a sum of the concentration of the NV center and P1 center) in diamond. However, a systematic experimental study of the spin concentration dependence of the coherence time was still missing. Here, we experimentally and theoretically investigate the Hahn echo decay curve with several diamond samples with different spin concentration. The Hahn echo results show that we observe a non-exponential decay for the low spin concentration while an exponential decay is dominant for the high spin concentration. By fitting the decay curve with a theoretical model, we show that both the amplitude and correlation time of the environmental noise have a clear dependence on the spin concentration. These results are essential to optimize the NV center concentration as high-performance quantum devices, particularly as quantum sensors.},
 pages = {054708-1--054708-6},
 title = {Experimental and Theoretical Analysis of Noise Strength and Environmental Correlation Time for Ensembles of Nitrogen-Vacancy Centers in Diamond},
 volume = {89},
 year = {2020}
}