Mid-Infrared Quantum Imaging and Spectroscopy

我的研究计划的中心目标是开创和建立基于诱导量子相干的中红外量子光谱学和量子光谱成像。量子增强传感是量子光学的一个生动发展的分支，它开始触及实际的、现实世界的应用。首先，它是从对传感和成像的经典极限以及如何用光的量子态来克服这些极限的基本见解中构思出来的，例如，它使人能够绕过阿贝斯著名的光学分辨率极限，并利用纠缠和非经典光子统计等量子资源来降低来自光的量子化(散粒噪声)的基本噪声。波长在2-20微米之间的中红外光具有巨大的科学和技术意义，因为它覆盖了最强烈和最明显的分子振动吸收带，例如重要气体分子或生物组织中特定化学基团的伸缩模式。这使得它非常适合于分子光谱学和光谱成像，从而在化学或生物医学研究和诊断中有广泛的用途。然而，现实世界中的中IR应用存在严重的技术障碍。主要原因是中红外探测器、相机和光谱仪在可见光波段的性能基本上比硅基探测器差许多个数量级，这对灵敏度、动态范围、信噪比、捕获时间以及时间和空间分辨率造成了严重的限制。此外，尽管在量子级联激光器、中红外超连续谱光源、中红外频率梳或中红外同步辐射方面取得了有希望的进展，但商业上可用的中红外光源和明亮的中红外光源比它们的可见光波长激光器(如激光二极管)要复杂得多，成本密集，而且不那么健壮。基于量子光学，我的研究计划旨在完全克服这些限制，在中红外不需要任何探测器或激光光源，只使用在可见光下敏感的高性能相机和探测器。这是由最近引入的一种量子光学方法实现的，该方法使用诱导量子相干来对未被检测到的光子进行量子成像(自然512,409,2014)。实施中红外量子成像和光谱学不仅将从根本上有趣地开辟量子光学的全新波长体系，而且将在化学传感、生物分析或医疗诊断中的广泛应用中具有高度相关性。一个显著的例子和第一个目标应用是与癌症诊断相关的组织的无标记、化学选择性的中红外显微镜。此外，由于这种方法本质上依赖于量子纠缠，它自然为量子增强分辨率和亚散粒噪声性能以及研究非常敏感的样品所需的超弱光级照明开辟了道路。

The central goal of my research plan is pioneering and establishing mid-infrared quantum spectroscopy and quantum spectral-imaging based on induced quantum coherence. Quantum enhanced sensing is a vividly developing branch of quantum optics that starts touching on practical, real-world applications. First conceived from fundamental insights on the classical limits of sensing and imaging and how to overcome them with quantum states of light it enables for example to bypass Abbes famous optical resolution limit and to reduce fundamental noise from the quantization of light (shot-noise) leveraging quantum resources like entanglement and nonclassical photon statistics. Mid-IR light between wavelengths of 2-20 um has tremendous scientific and technological relevance because it covers the most intense and distinct vibrational molecular absorption bands, e.g. of important gas molecules or stretching modes of specific chemical groups in biological tissues. This makes it excellently suited for molecular spectroscopy and spectral imaging leading to a wide range of uses in chemical or bio-medical research and diagnostics. However, there are severe technological roadblocks for real-world mid-IR applications. The dominant reason is that detectors, cameras and spectrometers for the mid-infrared fundamentally have many orders of magnitude worse performance than their Si-based counterparts in the visible wavelength regime imposing serious limitations on sensitivity, dynamic range, signal-to-noise ratio, acquisition time, and temporal and spatial resolution. Moreover, despite promising progress for quantum cascade lasers, mid-IR super-continuum sources, mid-IR frequency combs or mid-IR synchrotron radiation, commercially available and bright sources of mid-infrared light are much more complex, cost-intensive, and less robust then their visible wavelength lasers such as laser diodes. Based on quantum optics, my research plan aims at fully overcoming these limitations, by not requiring any detectors or laser sources in the mid-IR, and using only high performance cameras and detectors sensitive in the visible. This is enabled by a recently introduced quantum optics approach using induced quantum coherence for quantum imaging with undetected photons (Nature 512, 409, 2014). Implementing mid-IR quantum imaging and spectroscopy will not only be fundamentally interesting opening up an entirely new wavelength regime for quantum optics but will be highly relevant for a wide range of applications in chemical sensing, biological analysis or medical diagnostics. A striking example and first target application is label-free, chemically selective mid-IR microscopy of tissues relevant for cancer diagnostics. Moreover, because this approach relies intrinsically on quantum entanglement it naturally opens up avenues for quantum enhanced resolution and sub-shot-noise performance, as well as for ultra-low light level illumination important for studying very sensitive samples.