New Color Centers in Diamond: Towards Broadband Quantum Memories

信息技术是社会的主要支柱之一，信息安全变得越来越重要。利用量子通信线路是提高未来信息系统安全性的一个方向。根据自然法则，这样的线路不允许对传输的信息进行不可追踪的复制。但是，使它们安全的物理原理（即不可克隆定理）也禁止使用经典中继器，这反过来限制了通信距离和速度。这个问题可以通过使用量子中继器来解决，量子中继器的关键成分是量子存储设备。本项目旨在开发一种基于钻石色心量子态的新型固态量子存储器。该项目将利用德克萨斯农工大学在内存访问协议及其物理实现方面取得的理论和实验进展。该研究项目将加强美国在基于光学集成的固态量子存储器领域的存在。它还将有助于培养这个动态发展的跨学科研究领域的下一代科学家。研究生和本科生将通过参与实验、建立理论模型、编程、收集和解释实验数据以及数值模拟来参与调查。调查人员还将把获得的结果纳入课程。本项目重点研究新的色中心，即金刚石中的锗空位和硅空位（GeV和SiV），以开拓基于集成的金刚石宽带量子存储器的实验实现。这种实现将使用一种基于控制场的离散空间啁啾的量子存储器新方法来实现，该方法最近由co- pi提出。这项工作的结果是一个单光子固态接口，将成为可扩展通用光学量子计算机道路上的一个里程碑。与现有技术相比，如稀土掺杂晶体和金刚石中的氮空位中心（NV）， SiV和GeV具有更强的光相互作用和更少的光谱扩散（以及不均匀的线宽）。更强的零声子线使单个光子与单个硅空位的相互作用更有效，而窄的非均匀线展宽有利于基于集成的量子存储器。GeV和SiV的其他优点是存在极化选择规则和基态大（分别为160 GHz和50 GHz）的能级分裂。最后一种允许大的存储带宽。值得指出的是，多ghz vs MHz带宽是光学量子网络优于RF量子网络（即超导电路（SCC））的关键优势。GeV和SiV的唯一缺点是电子自旋相干时间较短。然而，研究表明，通过将SiV冷却到100马克，这一时间可以显著增加到13毫秒。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.