Taming Entangled Photons: Programmable Control of Quantum States of Light

驯服纠缠的光子：光的量子态的可编程控制没有量子力学的奇怪之处比纠缠粒子的行为更明显；测量一个粒子的状态可以影响它的纠缠伙伴的状态，即使这两个粒子相隔很远。这些奇怪的特性掩盖了我们关于世界如何运行的常识概念，但它们可能会被引导到现实世界的应用程序中，以获得巨大的利益。一种这样的可能性是量子密钥分发(QKD)，它依靠量子力学定律在两个远程各方之间的信息传输中提供无条件的安全。在一个日益依赖通信安全的现代世界中，大规模量子密钥分发是当前研究的一个主要目标。在这一目标的推动下，我们正在探索基于光脉冲整形的操作和测量纠缠光子的新方法。在标准脉冲整形器中，可编程地操纵输入场的不同频率分量以在输出端创建用户定义的光学波形。通过大幅扩展这种脉冲整形思想来控制纠缠光子实验中涉及的场，我们不仅看到了研究新物理的机会，而且还扩展了现有的从单个光量子中印记和提取信息的能力，为安全的高速通信提供了新的可能性，并有望为更安全的明天做出贡献。具体地说，我们将重点介绍如何利用经典光场的脉冲整形来改进(1)探测和(2)产生纠缠光子。通常，单光子探测是通过具有比被测量的光子持续时间长得多的时间分辨率的光电二极管来实现的，这意味着时间自由度中的精细特征是不可观测的。因此，我们正在努力扩展一种不同的探测方案，在该方案中，每个光子与一个超短飞秒脉冲混合；然后，如果光子通过和频产生与脉冲结合，就有可能确定其到达时间，使其在短脉冲本身的持续时间内，允许在飞秒时间尺度上的分辨率，并提供访问频率-时间纠缠光子的巨大信息潜力。我们的计划是在这一领域的前人工作的基础上大幅扩展，并实现一个用于飞秒探测的光纤兼容系统，在各种经典领域进行实验。我们将探索在光子态表征、非局域量子效应的演示和新的量子密钥分发协议中使用这种检测的可能性。在这个提议的第二个主要方向中，我们将考虑不用于探测的经典场的整形，而是用于产生纠缠光子的整形。通过下转换产生纠缠光子的泵浦光场的光谱-时间性质可以对所产生的量子态的性质产生深远的影响，并且可以通过可编程的脉冲整形来主动更新，这对我们来说是重要的。特别是，我们计划考虑光学频率梳及其产生新形式纠缠态的潜力，将用于光通信的梳状技术与有趣的量子应用相结合。

Taming Entangled Photons: Programmable Control of Quantum States of LightNowhere is the strangeness of quantum mechanics more evident than in the behavior of entangled particles; measuring the state of one particle can influence that of its entangled partner, even if the pair are distantly separated. Such weird properties belie our common-sense notions of how the world works, and yet they can potentially be channeled for tremendous benefit in real-world applications. One such possibility is quantum key distribution (QKD), which relies on the laws of quantum mechanics to offer unconditional security in the transmission of information between two remote parties. In a modern world increasingly dependent on communication security, large-scale QKD represents a major goal of current research. Motivated by this objective, we are exploring new ways to manipulate and measure entangled photons based on optical pulse shaping. In a standard pulse shaper, the different frequency components of an input field are programmably manipulated to create a user-defined optical waveform at the output. By significantly extending such pulse-shaping ideas for controlling the fields involved in entangled photon experiments, we see opportunity not only to investigate new physics, but also to expand on current capabilities for imprinting and extracting information from individual light quanta, offering new possibilities for secure high-speed communications and hopefully contributing to a safer tomorrow.Specifically, we will focus on ways to use pulse shaping of classical fields for advances in (1) detection and (2) generation of entangled photons. Typically, single-photon detection is achieved with photodiodes possessing timing resolutions much longer than the duration of the photons being measured, meaning that the fine features in the temporal degree of freedom are unobservable. Accordingly, we are working to expand on a different detection scheme in which each photon is mixed with an ultrashort femtosecond pulse; then if the photon combines with the pulse through sum-frequency generation, it is possible to determine its arrival time to within the duration of the short pulse itself, permitting resolution on the femtosecond timescale and giving access to the vast information potential of frequency-time entangled photons. Our plan is to significantly expand on previous work in this area and implement an optical-fiber-compatible system for femtosecond detection, experimenting with a variety of classical fields. We will explore the possibilities for utilizing such detection in photon state characterization, demonstration of nonlocal quantum effects, and new QKD protocols. In the second major direction of this proposal, we will consider shaping of classical fields used not for detection, but rather generation of entangled photons. The spectro-temporal properties of the pump fields which produce entangled photons through downconversion can have a profound impact on the nature of the generated quantum state and "importantly for us" can be actively updated through programmable pulse shaping. In particular, we plan to consider optical frequency combs and their potential for generating new forms of entangled states, merging comb technology for optical communications with interesting quantum applications.