Methods and Applications of Multi-Photon Quantum State Synthesis

我们正在开发一种有效地创建各种单光子态和多光子态的源。该项目是PI过去在优化设计的自发参数下转换源、高效率光子探测器和低损耗高速光路方面研究的成果。具体地说，该项目实现了一种切换的、时间上多路复用的方案，允许近乎确定地准备单光子态。将四个这样的态组合在一起，实现了第一代高效的纠缠光子对，这是量子信息处理中许多协议的关键资源。此外，该方案的一般化使得能够制备各种其他感兴趣的多光子状态。例如，我们可以制备电磁场的精确能量本征态，即“Fock态”，比目前依赖于不可能事件同时发生的方案的效率要高出指数倍；事实上，在无损光学和完美探测器的限制下，该方法是100%有效的。我们正在研究的核心概念--一次增加(或减少)一个光子的能力--可能进一步扩展到能够产生其他感兴趣的多光子状态。从量子力学的基础测试到光量子计算，从量子密码学到纠缠增强的量子计量学，单光子和纠缠光子已经成为实验的中心资源。尽管最近取得了进展，但可靠和确定地创建即使是简单的光学状态，例如按需单光子，仍然具有挑战性。虽然已经提出了实现更复杂的多光子状态的方案，但这些方案通常与处于这种状态的光子数量成指数级地不匹配。因此，在这种类型的实验中，观测到的速率随着所需光子数量的增加而非常迅速地下降，需要几分钟或几个小时才能观察到所需状态的一个实例。我们正在追求高效地创造各种单光子态和多光子态，推动量子信息处理在几个不同领域的前沿，包括量子通信、量子计量学和量子计算。除了探索实现真正的单光子态和多光子态的潜在变革性方法外，该项目还有可能在量子信息处理的“传统”领域之外产生更广泛的影响，例如在单光子水平上的人类视觉研究。在更小的年龄和更广泛的场所将基本量子信息现象的现实带给学生，激发他们在STEM领域进一步学习知识的兴趣。

We are developing a source for efficient creation of various single- and multi-photon states. This project is a culmination of the PI's past research on optimally engineered spontaneous parametric downconversion sources, high-efficiency photon detectors, and low-loss high-speed optical circuits. Specifically, the project implements a switched, temporally-multiplexed scheme that allows near-deterministic preparation of single-photon states. Combining four such states realizes the first efficient generation of heralded entangled photon pairs, a critical resource for many protocols in quantum information processing. Moreover, generalizations of the scheme enable preparation of a variety of other multi-photon states of interest. For instance, we can prepare exact energy eigenstates of the electromagnetic field, "Fock states," exponentially more efficiently than with present schemes relying on the simultaneous occurrence of improbable events; in fact, in the limit of lossless optics and perfect detectors, the method is 100% efficient. The central concept -- the ability to add (or subtract) photons one at a time -- can potentially be further extended to enable production of other multi-photon states of interest as well, as we are investigating. Single and entangled photons have become a central resource for experiments ranging from fundamental tests of quantum mechanics to optical quantum computing, from quantum cryptography to entanglement-enhanced quantum metrology. Despite recent advances, reliably and deterministically creating even simple optical states, e.g., single photons on demand, remains challenging. And while schemes to realize more complicated multi-photon states have been proposed, these typically scale exponentially poorly with the number of photons in this state. As a result, observed rates in experiments of this sort drop very quickly as the number of required photons increases, requiring minutes or hours to observe a single instance of the desired state. We are pursuing the efficient creation of various single- and multi-photon states, pushing the frontiers of quantum information processing in several different areas, including quantum communication, quantum metrology, and quantum computing. In addition to exploring a potentially transformative method for realizing true single- and multi-photon states, this project has the potential for broader impact beyond the "traditional" areas of quantum information processing, e.g., for human vision studies at the single-photon level. Bringing the realities of basic quantum information phenomena to students at an earlier age and in broader venues stimulates their interest in pursuing further knowledge in STEM areas.