ONAIR · On-chip quantum absorption spectroscopy in the infrared

11.6% of world deaths are related to air pollution. The first step to tackle this problem is mapping the air quality with high resolution on a large scale. This task requires a distributed network of miniaturized, inexpensive and efficient gas sensors, not available today. In our project, we aim at demonstrating a new quantum sensing measurement scheme on a photonic chip. This would enable low cost, mm2 footprint and efficient gas detection, suitable for distributed sensing networks.The quantum process at the basis of our sensing proposal is called “undetected photon quantum spectroscopy (UPQS)”, where entangled photon pairs are used, one of them in the visible (VIS) while the other in the mid infrared (MIR) range. UPQS exploits the indistinguishability between two sources of entangled pairs. By measuring the visible photon, one can realise MIR absorption spectroscopy without the need of measuring the MIR photon. In this way, it is possible to overcome the limitations of MIR technologies while having access to the nonpareil spectral information of the MIR range, where molecules exhibit unique and strong vibrational absorption bands.The proposed project will demonstrate UPQS on a silicon chip, for the first time. By leveraging the maturity of CMOS technology and silicon platform, the new UPQS scheme would enable a new class of sensors, integrable on smart devices and accessible to the scientific and technology community at large. The vision is to enable new devices for a wide range of applications, from industry to medicine, and to make possible a new approach to distribute sensing for highly resolved air quality monitoring. Moreover, the demonstration of on-chip UPQS would provide new insights into integrated quantum photonics, MIR photonics and quantum sensing, developing a platform for fundamentally new lines of research in fundamental and applied quantum photonics.