New Color Centers in Diamond: Towards Broadband Quantum Memories

信息技术是社会的主要支柱之一，信息安全正变得越来越重要。提高未来信息系统安全性的一个方向是利用量子通信线路。根据自然规律，这样的线路不允许对所传输的信息进行不可追踪的复制。但使它们安全的同一物理原理(即非克隆定理)也禁止使用经典中继器，这反过来又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。本项目的目的是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开发的理论和实验进展。这一研究项目将加强美国在基于光学系综的固态量子存储器领域的存在。它还将帮助培训这一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、开发理论模型、编程、收集和解释实验数据以及数值模拟来参与调查。研究人员还将把所获得的结果融入到课程中。该项目专注于新的色心，即钻石中的锗空位和硅空位(GeV和SIV)，以开创性地在钻石中实现基于系综的宽带量子存储。这一实现将使用一种新的量子存储方法来实现，该方法基于最近由联合PI提出的控制场的离散空间啁啾。这项工作的成果--单光子固态接口--将是迈向可扩展通用光量子计算机道路上的一个里程碑。与现有的稀土掺杂晶体和金刚石(NV)中的氮空位中心等技术相比，SIV和GeV具有更强的光学相互作用和更小的光谱扩散(以及不均匀的线宽)。较强的零声子线提供了更有效的单光子与单硅空位的相互作用，而窄的非均匀线宽有利于基于系综的量子存储。GeV和SIV的其他优点是存在偏振选择规则和基态中的大(相应的160 GHz和50 GHz)能级分裂。最后一种支持大容量存储带宽。值得指出的是，多GHz与MHz带宽是光网络相对于射频量子网络(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，已经表明，通过将SIV冷却到100 mK，可以大幅增加这一时间，最高可达13ms。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势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.