NW/1: Mid-Infrared Quantum Imaging and Spectroscopy

The central goal of the project 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 Abbe’s famous optical resolution limit and to reduce fundamental noise from the quantisation of light (shot-noise) leveraging quantum resources like entanglement and non-classical photon statistics. Mid-IR light between wavelengths of 2-20 μm 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 a 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.