Entangled Photon Pairs on Demand

量子纠缠的概念一直是量子信息科学（QIS）革命的关键驱动力。纠缠粒子显示出比经典物理学所允许的任何东西都更强的相关性，并且可以作为量子增强技术的强大资源。虽然现在已经在许多不同的物理系统中观察到纠缠，包括电子、原子和光子，但在产生和控制纠缠粒子方面的重大进展对实验量子信息系统的发展至关重要。例如，纠缠光子具有各种理想的特性，可以在量子通信、量子传感和量子计算中实现应用。然而，最广泛使用和高质量的纠缠光子源是基于一个固有的随机过程，很少发射光子对。该项目旨在克服这种随机性，并根据需要开发一种真正的“按钮”纠缠光子对源。这种源的实现将推动当前基于纠缠的光子QIS实验从“原理验证”实验室演示到实际的现实世界QIS应用。与此同时，对这种按需来源背后的基础物理学的研究将有助于推进我们目前对量子科学的理解的国家利益。该项目还为研究生和本科生提供教育和研究经验。这是培养下一代QIS科学家的绝佳机会。该方法基于参数下转换（PDC）的使用，这是一种已知可以产生高质量纠缠光子对的过程，但以完全随机的方式。核心思想是通过使用线性光学量子计算（LOQC）范式的技术，结合鲁棒周期性量子存储器（CQM）设备，将几个随机的PDC对组合成一个有用的对，来克服这种固有的随机性。粗略地说，在发射光子的子集上进行的破坏性loqc型测量用于概率地“预示”剩余光子对的存在。然后，这一对被主动切换到两个基于环路的CQM设备中，在保持光子纠缠的同时安全地存储光子。当需要时，纠缠对可以按需释放。“按钮”操作)。实验方法包括使用同步超快脉冲PDC源，基于量子干涉效应和单光子探测的预警信号，以及基于高速电光的开关和存储环路。在许多方面，这种按需纠缠光子对的源可以被视为一种小型的专用LOQC设备，在QIS中具有许多实际应用。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。

The concept of quantum entanglement has been a key driving force of the Quantum Information Science (QIS) revolution. Entangled particles display correlations that are stronger than anything allowed by classical physics, and can serve as a powerful resource for quantum-enhanced technologies. Although entanglement has now been observed in a number of different physical systems—including electrons, atoms, and photons—significant advances in the production and control of entangled particles are crucial for the advancement of experimental QIS. Entangled photons, for example, possess a variety of desirable properties that may enable applications in quantum communications, quantum sensing, and quantum computing. However, the most widely used and high-quality source of entangled photons is based on an inherently random process that only rarely emits photon pairs. This project aims to overcome this randomness and develop a true “push-button” source of entangled photon pairs on demand. The realization of such a source will advance current entanglement-based photonic QIS experiments from “proof-of-principle” laboratory demonstrations towards practical real-world QIS applications. At the same time, investigations of the fundamental physics behind this on-demand source will serve the national interest of progressing our current understanding of quantum science. The project also provides education and research experience for both graduate and undergraduate students. This represents an outstanding opportunity for training the next generation of QIS scientists.The approach is based on the use of Parametric Down Conversion (PDC)—a process that is known to produce high-quality entangled photon pairs, but in a completely random fashion. The core idea is to overcome this inherent randomness by combining several random PDC pairs into one useful pair using techniques from the Linear Optics Quantum Computing (LOQC) paradigm, coupled with robust Cyclical Quantum Memory (CQM) devices. Roughly speaking, destructive LOQC-type measurements performed on a subset of the emitted photons are used to probabilistically “herald” the presence of exactly one remaining pair. The heralded pair is then actively switched into two loop-based CQM devices, which safely store the photons while maintaining their entanglement. The entangled pair can then be released on-demand when needed (ie. “push-button” operation). The experimental methods to be employed involve the use of synchronized ultrafast pulsed PDC sources, heralding signals based on quantum interference effects and single-photon detection, and high-speed electro-optic-based switching and storage loops. In many ways, this source of entangled photon pairs on-demand can be viewed as a small-scale special-purpose LOQC device with numerous practical applications in QIS.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.