New Color Centers in Diamond: Towards Broadband Quantum Memories
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Information technologies are among the main pillars of society, and information security is becoming more important. One direction for improving the security of future information systems is to utilize quantum communication lines. Based on laws of nature, such lines do not allow non-traceable copying of the information transmitted. But the same physics that makes them secure (i.e. the non-cloning theorem) also forbids the use of classical repeaters, which in turn limits communication distance and speed. This issue may be overcome by using quantum repeaters, the key ingredient of which is a quantum memory device. The aim of this project is to develop a novel solid-state quantum memory based on quantum states of color centers in diamond. This project will utilize theoretical and experimental advances developed at Texas A&M University both for the memory access protocol and for its physical implementation. This research project will strengthen the US presence in the field of optical ensemble-based solid-state quantum memories. It will also help train the next generation of scientists in this dynamically developing interdisciplinary field of research. Graduate and undergraduate students will get involved in the investigations through participation in the experiments, developing theoretical models, programming, collecting and interpreting experimental data, and numerical simulations. The investigators will also incorporate the obtained results into courses.This project focuses on new color centers, namely, Germanium Vacancies and Silicon Vacancies in diamond (GeV and SiV) for pioneering experimental realization of an ensemble based broadband quantum memory in diamond. This realization will be achieved using a new approach to quantum memory based on a discrete spatial chirp of a control field that has recently been suggested by the co-PIs. The outcome of this work, a single-photon solid-state interface, will be a milestone on the way to a scalable universal optical quantum computer. In comparison to existing technologies, like rare-earth doped crystals and nitrogen vacancy centers in diamond (NV), SiV and GeV have stronger optical interaction and less spectral diffusion (and inhomogeneous linewidths). The stronger zero-phonon line gives more efficient interaction of a single photon with a single silicon-vacancy, while a narrow inhomogeneous line broadening favors ensemble-based quantum memories. Other advantages of GeV and SiV are the presence of polarization selection rules and large (160 GHz and 50 GHz accordingly) energy level splitting in the ground state. The last one allows for large storage bandwidth. It is worth pointing out that multi-GHz vs MHz bandwidth is a key advantage of an optical over RF quantum networks (i.e. superconducting circuits (SCC)). The only disadvantage of GeV and SiV is a shorter electron-spin coherence time. However, it has been shown that this can be dramatically increased, up to 13 ms, by cooling SiV down to 100 mK.This award reflects NSF''s statutory mission and has been deemed worthy of support through evaluation using the Foundation''s intellectual merit and broader impacts review criteria.