Abstract
Infrared absorption sensing is a widely adopted technique for gas concentration sensing in environmental monitoring, industrial inspection, and safety applications. However, the precision of concentration estimation based on classical optical probes is fundamentally limited by shot noise. Here, we demonstrate a gas concentration sensing approach using quantum-correlated photon pairs generated via spontaneous parametric down-conversion. Acetylene is employed as a benchmark analyte to characterize the concentration–transmittance relationship and to evaluate sensing precision over its explosive concentration range. Compared with an ideal coherent-state probe having the same mean photon number, the quantum protocol achieves sub-shot-noise performance in concentration estimation. Our results establish a practical framework for applying quantum-correlated light to high-precision gas concentration sensing and open new opportunities for quantum infrared gas sensing.