ERI: Study of quantum entanglement and spatially different photon pair generation through intermodal four-wave mixing in few-mode and multimode fibers

随着对安全量子通信系统与光通信系统相结合的需求持续增长，利用空间分复用（SDM）扩大电信系统容量的努力正在进行。通过当前的光通信网络或未来的SDM系统传播光的量子态可以满足这一需求，并满足消费者对安全通信的基本要求。本研究的首要目标是通过光纤上纠缠光子的产生和传输来推进这一目标。在过去，纠缠光子对是利用块状周期性极化晶体和利用二阶非线性的波导产生的。然而，这种方法会导致光纤耦合带来的额外损耗，并且在电信带宽下存在光子产率低的问题。通过光纤产生和传输纠缠光子是各种应用所需要的。然而，目前的方法面临着一些挑战，包括复杂性，有限的数据生成，对笨重和高功率脉冲激光器的依赖，以及量子噪声的引入。本研究提出利用少模和多模光纤的各种模式来产生一对纠缠光子，这将提供对纠缠特性的更好控制，并更好地与SDM系统集成。这种方法有望减轻前面提到的挑战。作为研究和教育整合的一部分，从事该项目的研究生将接受非线性光纤和量子激光源的培训。此外，本科生将有机会通过研究学分和暑期实习参与项目的各个阶段，以激发他们对密苏里大学光纤研究的兴趣。密苏里大学是一所少数民族服务的大学。本研究旨在探讨多模和少模光纤中多模非线性对量子纠缠的影响。这个项目既重要又创新，因为它将利用多模态非线性在这种光纤中产生和传输跨越各种空间模式的量子信道。通过在光纤的两种不同模式中使用泵浦，自发的四波混频非线性效应产生了在不同通道中处于不同空间模式的纠缠光子对。该项目旨在建立理论和实验平台来研究这种多式联运纠缠模式产生的潜在机制。这些平台将用于检查光纤中这种多模态缠结的基本过程。随后的量子相关实验将进行表征所产生的光子对量子态。通过在光纤中直接产生纠缠光子对，可以消除耦合损耗；通过选择光纤和泵浦波长，可以避免拉曼散射噪声。主要目标是通过在少模和多模光纤中利用多模量子纠缠来改善光纤上的量子通信，并可能对利用sdm兼容光纤的量子通信和传感产生变革性影响。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。

Substantial efforts are underway to expand the capacity of telecommunication systems utilizing spatial division multiplexing (SDM) as the demand for secure quantum communication systems combined with optical communication systems continues to grow. Propagating quantum states of light through current optical communication networks or future SDM systems can fulfill this demand and meet the essential consumer requirements for secure communication. The overarching aim of this research is to advance this objective through the Production and transmission of entangled photons over optical fibers. In the past, entangled photon pairs were created using bulk periodically poled crystals and waveguides utilizing their second-order nonlinearity. However, this method results in additional loss from fiber coupling and suffers from low photon yield at telecommunication bandwidths. The generation and transmission of entangled photons through optical fibers are desirable for a variety of applications. Nevertheless, the current approaches pose several challenges, including complexity, limited data generation, reliance on bulky and high-powered pulsed lasers, and the introduction of quantum noise. This study proposes the utilization of various modes of few-mode and multimode fibers to produce a pair of entangled photons, which will provide improved control over entanglement properties and better integration with SDM systems. This approach is expected to alleviate the challenges mentioned earlier. As part of the research and education integration, a graduate student working on this project will receive training in nonlinear fiber optics and quantum laser sources. Furthermore, undergraduate students will have the opportunity to participate in various stages of the project through research credits and summer internships in order to spark their interest in fiber-optic research at Missouri S&T, which is a minority-serving university.The proposed research aims to investigate the impact of intermodal nonlinearities on quantum entanglement in few-mode and multimode fibers. This project is both significant and innovative in that it will employ intermodal nonlinearities to generate and transmit quantum channels across various spatial modes within such fibers. By employing pumps in two different modes of the fiber, spontaneous four-wave mixing nonlinear effect generates an entangled photon pair each of which are in a different spatial mode traveling in different channels. The project seeks to establish theoretical and experimental platforms to investigate the underlying mechanisms of such intermodal entangled mode generation. These platforms will be utilized to examine the basic processes of such intermodal entanglement in fibers. Subsequent quantum correlation experiments will be performed to characterize the generated photon pairs quantum states. By directly generating entangled photon pairs in fiber, the coupling loss will be eliminated and by the choice of fiber and the pump wavelengths, the Raman scattering noise can be avoided. The primary objective is to improve quantum communication over fiber by utilizing intermodal quantum entanglement in few-mode and multimode fibers and could have a transformative impact on quantum communication and sensing utilizing SDM-compatible fibers.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.