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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Generation of Polarization Entangled Photon Pairs in the Mid-Infrared and Visible Regions

Haruya Hirota, Koichiro Tanaka

Published Jun 23, 2025• 0 citations

Abstract

Photon entanglement is essential for quantum communication, sensing, and computing. While research on frequency-degenerate entangled photons in the near-infrared (NIR) region has advanced significantly, entangled light spanning mid-infrared (MIR) and visible (VIS) frequencies remains under development [1]. For instance, in the MIR region, chiral collective lattice vibration modes that exhibit selectivity for circularly polarized light have been observed in two-dimensional layered materials [2], suggesting the existence of quantum entanglement with electronic states [3]. This entanglement could lead to the conservation of quantum states. For this purpose, it is necessary to generate quantum entangled states of photons in the MIR and VIS regions with high fidelity.

DOI: 10.1109/cleo/europe-eqec65582.2025.11111389

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The mid-infrared (MIR) region of the electromagnetic spectrum spans from 2- to 25-

μ\mathrm{m}

, serving as a valuable tool for accessing rich chemical information. Functional groups, lipids, and other complex molecules can be analyzed by optical absorption measurements due to their vibrational modes in the MIR spectral region. Over the past few decades, this field has faced challenges due to difficulties in generating MIR light and the limited maturity of detection systems in this spectral range. Quantum imaging with undetected light (QIUL) provides a spectrally tuneable photon-pair source, in which the sample can be illuminated with MIR light while visible (VIS) light is employed for detection and image reconstruction, overcoming the detection limitations and benefiting from the rich chemical information of the MIR spectral region. All previous QIUL implementations are based on spatial correlations, which are never perfect and thus hindered the imaging performance. In this work, we implement a raster-scanning QIUL method that is independent of the strength of the spatial correlations and achieves a spatial resolution beyond the limitations of these correlations.