EAGER: Spatial-Mode Entanglement and Spatial-Mode-Selective Quantum Frequency Conversion in Few-Mode Fibers

光纤损耗限制了长距离量子通信链路的数据传输速率，这对于安全信息交换和未来的量子云计算至关重要。提高量子通信速率的唯一方法是增加传输光子所使用的自由度（模式）。虽然偏振和频率自由度已经被广泛探索，但将量子信息编码到低损耗少模光纤中传播的空间模式（光束轮廓）中迄今为止很少受到关注。该项目旨在改变这种情况，通过直接在光纤内部实现空间量子信息的编码器和解码器，为量子通信开放空间自由度。开放大量的空间自由度将大大提高量子通信速率，并使许多未来的长距离量子网络应用成为可能。此外，所开发的空间模式选择技术也可以在经典电信中找到其用途，例如，在模式解复用或在空间和频率模式之间的信息传输中。该项目将培养两名学生在非线性光学，量子信息处理和光通信。UTA是一个为少数民族服务的机构，我们将通过开放实验室活动和视觉上吸引人的演示来激发本科生和K-12学生对光子学的兴趣。技术说明这个探索性项目的目标是实现在空间多模或少模光纤上传输和接收量子信息所必需的两个关键功能-空间纠缠光子对产生和空间模-选择性量子频率转换-直接在少模光纤（FMF）中通过模间四波混频实现。通过在两个FMF模式中使用泵浦，我们将在这两个正交的空间模式中产生信号-空闲光子对。FMF相位匹配条件将使得能够在每个模式中由双波长泵浦驱动的两个同时的FWM过程，这可以适于实现上述两种功能。与依赖于奇异多模波导中的二阶非线性的先前方法不同，直接在FMF中实现这种空间量子信息处理功能消除了任何耦合损耗和串扰，并且利用了已经商业上可获得的并且还可以由许多供应商和研究机构广泛定制的FMF介质。该奖项反映了NSF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。

Optical fiber loss limits the rate of data transmission of long-distance quantum communication links, which are essential for secure information exchange and future quantum cloud computing. The only way to scale up the quantum communication rate is by increasing the number of degrees of freedom (modes) used by the transmitted photons. While polarization and frequency degrees of freedom have already been extensively explored, encoding the quantum information into the spatial modes (beam profiles) propagating in low-loss few-mode fibers has received little attention so far. This project aims to change this situation and open the spatial degrees of freedom for quantum communications by implementing encoders and decoders of spatial quantum information directly inside the fiber. Opening up a large number of spatial degrees of freedom will dramatically increase quantum communication rates and enable many future long-distance quantum networking applications. In addition, the developed spatial-mode selection technology could find its use also in classical telecommunications, e.g., in mode demultiplexing or in transfer of information between spatial and frequency modes. This project will train two students in nonlinear optics, quantum information processing, and optical communications. UTA is a minority-serving institution, and we will stimulate the interest in photonics from undergraduates and K-12 students via Open Lab events and visually-appealing demos.Technical descriptionThe goal of this exploratory project is to realize two key functions necessary for transmitting and receiving quantum information over spatially-multimode or few-mode optical fibers - the spatially-entangled photon-pair generation and spatial-mode-selective quantum frequency conversion - directly in a few-mode fiber (FMF) by means of inter-modal four-wave mixing. By employing pumps in two FMF modes, we will generate a signal-idler photon pair in these two orthogonal spatial modes. The FMF phase-matching conditions will enable two simultaneous FWM processes driven by two-wavelength pumps in each of the modes, which can be adapted to realize both functions mentioned above. Implementation of this spatial-quantum-information-processing functionality directly in FMF, unlike the previous approaches relying on second-order nonlinearity in exotic multimode waveguides, eliminates any coupling loss and crosstalk and utilizes the FMF medium that is already available commercially and is also widely customizable by a number of vendors and research institutions. This work could have a transformative impact on high-capacity quantum communications by enabling spatially-multimode-fiber-based quantum links.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.