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

随着对与光通信系统相结合的安全量子通信系统的需求持续增长，利用空分复用(SDM)来扩展电信系统的容量的大量工作正在进行中。通过现有的光通信网络或未来的SDM系统传输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。这项研究的首要目标是通过在光纤上产生和传输纠缠光子来推进这一目标。在过去，纠缠光子对是利用它们的二阶非线性利用周期性极化的晶体和波导产生的。然而，这种方法会导致光纤耦合的额外损耗，并且在通信带宽上存在光子产生率低的问题。纠缠光子的产生和通过光纤的传输在各种应用中都是可取的。然而，目前的方法带来了几个挑战，包括复杂性、有限的数据生成、对庞大的高功率脉冲激光的依赖以及量子噪声的引入。这项研究提出了利用少模和多模光纤的各种模式来产生一对纠缠光子，这将改善对纠缠性质的控制，并更好地与SDM系统集成。这一方法有望缓解前面提到的挑战。作为研究和教育一体化的一部分，参与该项目的一名研究生将接受非线性光纤光学和量子激光光源方面的培训。此外，本科生将有机会通过研究学分和暑期实习来参与该项目的不同阶段，以激发他们对密苏里州S大学光纤研究的兴趣。该大学是一所少数族裔服务的大学。拟议的研究旨在调查少模和多模光纤中互模非线性对量子纠缠的影响。该项目具有重大意义和创新意义，因为它将使用模式间非线性来产生量子通道，并在此类光纤内的各种空间模式中传输量子通道。通过在光纤的两个不同模式下泵浦，自发的四波混频非线性效应产生了一个纠缠的光子对，每个光子对在不同的信道中以不同的空间模式传输。该项目试图建立理论和实验平台来研究这种多模纠缠模产生的潜在机制。这些平台将被用来研究光纤中这种模式间纠缠的基本过程。随后将进行量子关联实验，以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，并且通过选择光纤和泵浦波长，可以避免拉曼散射噪声。主要目标是通过利用少模和多模光纤中的模间量子纠缠来改善光纤上的量子通信，并可能对使用SDM兼容光纤的量子通信和传感产生革命性影响。该奖项反映了NSF的法定使命，并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。

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.