Mid-infrared frequency-domain optical coherence tomography with undetected photons

Quantum entanglement holds the promise to drive a paradigm shift in imaging and sensing. This thesis presents the first experimental demonstration of mid-infrared frequency-domain optical coherence tomography powered by quantum entanglement. By utilising large-dimensional spectral entanglement in a non-linear interferometer, we present measurement sensitivities comparable to the state-of-the-art in classical techniques while exposing the sample to 8 orders of magnitude less optical power. At the same time, the technological overhead is reduced compared with classical techniques, which in contrast to our approach require sophisticated and cost-intensive broadband sources and detection strategies. Instead, the entanglement-enabled solution presented here facilitates the use of standard, off-the-shelf components. We present 2D and 3D imaging of lossy, practical, real-world samples, achieving 20 μm lateral and 10 μm depth resolution with quantum light in the mid-IR. The results have immediate relevance for applications in non-destructive testing such as quality control of coating thicknesses, cultural heritage conservation and microfluidics.