Taming Entangled Photons: Programmable Control of Quantum States of Light

驯服纠缠光子：光的量子态的可编程控制没有比纠缠粒子的行为更明显的量子力学的奇异之处了；测量一个粒子的状态可以影响其纠缠伙伴的状态，即使这对粒子相隔很远。这些奇怪的属性与我们对世界如何运作的常识性概念相矛盾，但它们有可能在现实世界的应用中带来巨大的好处。其中一种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方之间的信息传输中提供无条件的安全性。在日益依赖通信安全的现代世界中，大规模QKD是当前研究的一个主要目标。在此目标的激励下，我们正在探索基于光脉冲整形的操纵和测量纠缠光子的新方法。在标准的脉冲整形器中，输入字段的不同频率分量被可编程地操纵，以在输出处创建用户定义的光波形。通过显著扩展这种控制纠缠光子实验中涉及的场的脉冲整形思想，我们不仅看到了研究新物理学的机会，而且还扩展了当前从单个光量子中印记和提取信息的能力，为安全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。具体来说，我们将关注如何利用经典场的脉冲整形来推进(1)探测和(2)产生纠缠光子。通常，单光子探测是通过光电二极管实现的，光电二极管具有比被测量光子的持续时间长得多的定时分辨率，这意味着时间自由度的精细特征是不可观察的。因此，我们正在努力扩展一种不同的检测方案，其中每个光子与超短飞秒脉冲混合；然后，如果光子通过和频产生与脉冲结合，就有可能在短脉冲本身的持续时间内确定其到达时间，从而允许在飞秒时间尺度上进行分辨率，并获得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先前工作的基础上进行重大扩展，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、非局部量子效应的演示和新的QKD协议中利用这种检测的可能性。在这个提议的第二个主要方向上，我们将考虑塑造经典场，而不是用于探测，而是用于产生纠缠光子。通过下转换产生纠缠光子的泵浦场的光谱-时间特性可以对所生成的量子态的性质产生深远的影响，并且“对我们来说重要的是”可以通过可编程脉冲整形主动更新。特别是，我们计划考虑光频率梳及其产生新形式纠缠态的潜力，将光通信梳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.