Prolongation of coherence time of 167Er for photon-electron coherent manipulation
Takehiko Tawara, NTT Basic Research Laboratories
We have succeeded in prolonging the coherence time T2 of the 167Er ion for optical transitions between hyperfine sublevels by isotopically purifying Er ions. This removes magnetic fluctuations induced by various Er isotopes except 167Er. The coherence time increased about 4 times (1.5 μs) compared with that of non-purified samples. The electronic states in the 4f orbital of the Er ion show an interaction with telecom-band photons and long energy relaxation time T1 (about 11 ms). Therefore, the Er doped material is a promising platform for the realization of electron coherent manipulation by a photon. However, T2, which restricts the manipulation efficiency, is usually much shorter (about 400 μs) than the theoretical limit (T2 ≤ 2T1) because of the fluctuation of the magnetic moment caused by the electron spin of Er itself and the nuclear spin of the host crystal. In this work, the obtained T2 does not still reach the T1 limit, but we also revealed that its origin is in magnetic fluctuations of the nuclear spin in the host crystal as measured by the spectral-hole burning technique. Currently, we are also developing the epitaxial growth of the magnetic-purified host crystal doped with Er ions on a Si substrate. We believe that these results contribute greatly to the realization of the photon-electron (spin) coherent manipulation operated by telecom-band photons.
Ref: T. Tawara, G. Mariani, K. Shimizu, H. Omi, S. Adachi, H. Gotoh, “Effect of isotopic purification on spectral-hole narrowing in 167Er3+ hyperfine transitions,” Appl. Phys. Express 10, 042801 (2017).