© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

arXiv:2607.16419

Remote Infrared Absorption Spectroscopy with Undetected Photons

Simon Neves, Fériel Armbruster, Jean-Pierre Wolf

quant-phphysics.opticsSubmitted Jul 17, 2026• Announced Jul 21, 2026• 0 citations• Revised Aug 17, 2026 (v3)

v1 · Jul 17, 2026 v2 · Jul 22, 2026 v3 · Aug 17, 2026

Abstract

We demonstrate a novel method for remote open-path Fourier-transform infrared spectroscopy with undetected photons. Similar to previous quantum spectroscopy works, a mid-infrared spectrum is reconstructed by detecting a near-infrared radiation only, thus bypassing important limitations of infrared detectors. Our study however relies on the co-propagation of the photon-pair and the pump-laser over the same optical path, which allows the probing of the open atmosphere over long distances. By sending the photons over unprecedented distances of up-to 43.4m in the outdoor atmosphere, we were able to detect butane released in the open-path, as well as natural atmospheric methane, thus demonstrating the first use of infrared spectroscopy with undetected photons for atmospheric measurements.

Comments: 21 pages, 10 figures

Related papers

Quantum Fourier Transform Infrared Spectroscopy: Evaluation, Benchmarking, and Prospects

Paul Gattinger, Andreas Wolfgang Schell, Sven Ramelow +2 more

Sensing with undetected photons has enabled new, unconventional approaches to Fourier transform infrared spectroscopy (FT-IR). Leveraging properties of non-degenerate entangled photon pairs, mid-infrared (mid-IR) information can be accessed in the near-infrared (near-IR) spectral domain to perform mid-IR spectroscopy with silicon-based detection schemes. Here, we address practical aspects of vibrational spectroscopy with undetected photons using a quantum FT-IR (QFT-IR) implementation. The system operates in the spectral range from around 3000 cm −1 to 2380 cm −1 (detection at around 12 500 cm −1 ) and possesses only 68 pW of mid-IR probing power for spectroscopic measurements with a power-dependence of the signal-to-noise ratio of 1.5 × 10 5 mW −1/2 . We evaluate the system’s short- and long-term stability and experimentally compare it to a commercial FT-IR instrument using Allan–Werle plots to benchmark our QFT-IR implementation’s overall performance and stability. In addition, comparative qualitative spectroscopic measurements of polymer thin films are performed using the QFT-IR spectrometer and a commercial FT-IR with identical resolution and integration times. Our results show under which conditions QFT-IR can practically be competitive or potentially outperform conventional FT-IR technology.

arXiv:2503.13233•Applied Spectroscopy•May 21, 2025•7 citations

Open-path detection of organic vapors via quantum infrared spectroscopy

Simon Neves, Adimulya Kartiyasa, Shayantani Ghosh +3 more

In recent years, quantum Fourier transform infrared (QFTIR) spectroscopy has emerged as an alternative to conventional absorption spectroscopy in the mid-infrared region of the spectrum. By harnessing induced coherence and spectral correlations of photon pairs in a nonlinear Michelson interferometer, this technique offers promising potential for the practical detection of organic gases. However, little research was conducted to bring QFTIR spectrometers closer to domestic or in-field usage. In this work, we present the first use of a QFTIR spectrometer for open-path detection of multiple interfering organic gases in ambient air. We built a nonlinear Michelson interferometer with 1.7 m-long arms to increase the absorption length, coupled with analysis techniques from classical differential absorption spectroscopy used for gas-traces detection. We thus characterize our spectrometer’s sensitivity to acetone, methanol, and ethanol vapors and demonstrate the accurate identification of mixtures of these gases released in ambient air. We show this characteristic is preserved over time by performing a measurement overnight and tracking the evolution of different gases’ average concentrations. These results constitute the first use-case of a QFTIR spectrometer as a detector of organic gases and, thus, represent an important milestone toward the development of such detectors in practical situations.

arXiv:2405.12822•APL Photonics•Sep 1, 2024•11 citations

Fourier-transform mid-IR hyperspectral imaging with undetected photons

Marlon Placke, Chiara Lindner, Inna Kviatkovsky +3 more

Quantum imaging with undetected photons allows measuring mid-infrared information with visible or near-infrared silicon-based light detection. We demonstrate a combination of quantum imaging and Fourier-transform spectral analysis for broadband high-resolution mid-infrared hyperspectral imaging.

•Jan 1, 2023•3 citations

Mid-IR hyperspectral imaging with undetected photons

Marlon Placke, Chiara Lindner, Felix Mann +4 more

By combining a nonlinear interferometer in imaging-mode with Fourier-transform spectroscopy, we realize broadband mid-infrared hyperspectral acquisition with undetected photons. We demonstrate the novel imaging technique on polymer and bio-tissue samples using only near-infrared silicon-based cameras.

Quantum 2.0 Conference and Exhibition•Jan 1, 2024•0 citations

High resolution Fourier-transform mid-infrared spectroscopy using nonlinear interferometers

Jachin Kunz, Chiara Lindner, Simon J. Herr +3 more

Nonlinear interferometers based on correlated photon pairs allow mid-infrared spectroscopy by measuring only near-infrared photons with a silicon-based detector, which offers higher detectivities than mid-infrared detectors. Here, we use the nonlinear interferometer not only to determine the transmission of a sample but also for spectral analysis - analogue to classical Fourier transform infrared (FTIR) spectrometers. The Quantum FTIR analyzes the absorption of gas mixtures with high spectral resolution over a broad mid-infrared wavelength range. Improved emission rates of the photon pair source yield sensitivities similar to a classical FTIR despite an extremely low light exposure on the sample.

Optical and Quantum Sensing and Precision Metrology II•Mar 8, 2023•1 citation

Fourier-Transform Infrared Spectroscopy with Near-Infrared Light

Chiara Lindner, Jachin Kunz, Simon J. Herr +3 more

Nonlinear interferometers using correlated photon pairs allow mid-infrared spectroscopy with near-infrared detection. In our work, we combine nonlinear interferom- etry with a measurement scheme and analysis in analogy to classical Fourier-transform spectroscopy, which enhances the spectroscopic performance.

OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES)•Jan 1, 2021•0 citations

We demonstrate a novel method for remote open-path Fourier-transform infrared spectroscopy with undetected photons. Similar to previous quantum spectroscopy works, a mid-infrared spectrum is reconstructed by detecting a near-infrared radiation only, thus bypassing important limitations of infrared detectors. Our study however relies on the co-propagation of the photon-pair and the pump-laser over the same optical path, which allows the probing of the open atmosphere over long distances. By sending the photons over unprecedented distances of up-to 43.4m in the outdoor atmosphere, we were able to detect butane released in the open-path, as well as natural atmospheric methane, thus demonstrating the first use of infrared spectroscopy with undetected photons for atmospheric measurements.

Sensing with undetected photons has enabled new, unconventional approaches to Fourier transform infrared spectroscopy (FT-IR). Leveraging properties of non-degenerate entangled photon pairs, mid-infrared (mid-IR) information can be accessed in the near-infrared (near-IR) spectral domain to perform mid-IR spectroscopy with silicon-based detection schemes. Here, we address practical aspects of vibrational spectroscopy with undetected photons using a quantum FT-IR (QFT-IR) implementation. The system operates in the spectral range from around 3000 cm −1 to 2380 cm −1 (detection at around 12 500 cm −1 ) and possesses only 68 pW of mid-IR probing power for spectroscopic measurements with a power-dependence of the signal-to-noise ratio of 1.5 × 10 5 mW −1/2 . We evaluate the system’s short- and long-term stability and experimentally compare it to a commercial FT-IR instrument using Allan–Werle plots to benchmark our QFT-IR implementation’s overall performance and stability. In addition, comparative qualitative spectroscopic measurements of polymer thin films are performed using the QFT-IR spectrometer and a commercial FT-IR with identical resolution and integration times. Our results show under which conditions QFT-IR can practically be competitive or potentially outperform conventional FT-IR technology.

In recent years, quantum Fourier transform infrared (QFTIR) spectroscopy has emerged as an alternative to conventional absorption spectroscopy in the mid-infrared region of the spectrum. By harnessing induced coherence and spectral correlations of photon pairs in a nonlinear Michelson interferometer, this technique offers promising potential for the practical detection of organic gases. However, little research was conducted to bring QFTIR spectrometers closer to domestic or in-field usage. In this work, we present the first use of a QFTIR spectrometer for open-path detection of multiple interfering organic gases in ambient air. We built a nonlinear Michelson interferometer with 1.7 m-long arms to increase the absorption length, coupled with analysis techniques from classical differential absorption spectroscopy used for gas-traces detection. We thus characterize our spectrometer’s sensitivity to acetone, methanol, and ethanol vapors and demonstrate the accurate identification of mixtures of these gases released in ambient air. We show this characteristic is preserved over time by performing a measurement overnight and tracking the evolution of different gases’ average concentrations. These results constitute the first use-case of a QFTIR spectrometer as a detector of organic gases and, thus, represent an important milestone toward the development of such detectors in practical situations.

Nonlinear interferometers based on correlated photon pairs allow mid-infrared spectroscopy by measuring only near-infrared photons with a silicon-based detector, which offers higher detectivities than mid-infrared detectors. Here, we use the nonlinear interferometer not only to determine the transmission of a sample but also for spectral analysis - analogue to classical Fourier transform infrared (FTIR) spectrometers. The Quantum FTIR analyzes the absorption of gas mixtures with high spectral resolution over a broad mid-infrared wavelength range. Improved emission rates of the photon pair source yield sensitivities similar to a classical FTIR despite an extremely low light exposure on the sample.