Grant: Alliance Grants

Emission of methane, a greenhouse gas, is a major contributor to climate change. Natural gas and oil pipeline leaks account for about 30% of methane emission. Early detection and mitigation of leaks will reduce emission, benefit the environment, and reduce energy costs. Sensor-carrying aircraft are utilized for pipeline monitoring, since they can quickly cover the vast and remote areas over which pipelines are spread. However, current airborne sensing technology is not sensitive enough to detect small emissions at a distance. Field tests show that state-of-the-art airborne standoff detection sensitivity is above1 kg/hour of methane emission, even under favourable weather conditions. Moreover, existing methods have a high rate of false positives and false negatives, particularly for low emission rates. The goal of this project is to develop and demonstrate airborne standoff quantum sensing of <1 kg/hour methane emission at a distance of 150 meters. At such a distance, the optical backscatter that returns to the aircraft is on the few-photon (quantum) level, even when using the highest laser power allowed for open beam operation. The challenge in detection of this weak signal is further compounded by strong background light from solar radiation. Current detection schemes rely on the weak optical absorption of methane at near-infrared frequencies, where they leverage mature near-infrared optical technology. However, at mid-infrared frequencies, methane absorption is 100 times stronger, and solar background is much lower, while detector noise is ~1000 time higher, and there are no detectors capable of few-photon detection. We plan to combine upconversion detection of mid-infrared light with threshold quantum photon number resolving detection. Mid-infrared sensing light is converted into near-infrared light, which can be detected with a thresholded quantum photon number resolving detector. Such detection has been shown to provide a quantum advantage in signal-to-noise ratio when detecting few-photon laser light in the presence of thermal background (such as solar radiation), due to the difference in the quantum properties of laser and thermal light.