Er sites in Si for quantum information processing

A. Lyasota, I. R. Berkman, G. G. de Boo, J. G. Bartholomew, S. Qi Lim, B. C. Johnson, J. C. McCallum, R. L. Ahlefeldt, M. J. Sellars, C. Yin, S. Rogge - Rare-earth ions in a solid-state host exhibit low homogeneous broadening and long spin coherence at cryogenic temperatures, making them promising for a range of quantum applications, such as optical quantum memories and optical-microwave transductions. Emitters in the telecom range with long electron spin and optical coherence in Si are especially attractive for quantum applications. Here, we report on the observation of Er sites in Si that have both long optical coherence and electron spin lifetime. We measured 1 ms spin coherence for two sites in a nuclear spin-free silicon crystal (<0.01% 29Si), which appeared to be instrumentally limited. Using dynamical decoupling we extended the spin coherence of one of the sites to 40 ms. Measurements with naturally abundant Si revealed that the Er electron spin coherence was limited by coupling to 29Si nuclear spins. The measured homogeneous linewidths of all sites are below 100 kHz, and inhomogeneous broadening approaches 100 MHz [1, 2]. Finally, integration into silicon on insulator nano-photonic devices is presented. The demonstration of a long spin coherence time and narrow optical linewidth in multiple sites show that Er in 28Si is an exceptional candidate for future quantum information and communication applications and can be used for single photon frequency multiplexing schemes.