Quantum Sensing for Highly Precise Gravity Measurement

The gravity of the earth’s surface is time and position-dependent, and precise information about the variation of the earth’s gravity over time can be crucial in many geophysical activities. For example, precise gravity information is useful in learning gravity fluctuations due to construction, oil, and mineral deposits, leading to a more accurate mapping of underground water currents, surveying, and satellite-free navigation systems. Similarly, gravity data can be used to detect changes in the sea level due to polar ice melting and seismic activities, which is extremely important for monitoring climate change. We often rely on satellite-based gravity maps to study the changes in gravity. However, satellite-based gravity maps are limited by spatial and temporal resolution, providing only milli-Gal order of precision on the gravity constant. For many geophysical applications, a micro-Gal level of precision is desirable. In this case, a ground-based gravity survey will improve the spatial and temporal resolution along with the precision of the absolute value of gravity. A potential technology providing ground-based, highly precise, and stable gravity measurements is Quantum Sensing. In this project, we will build a quantum sensing experiment based on cold atom interferometry (CAI) in the lab. We will blend the existing knowledge related to such interferometers with state-of-the-art optically engineered lasers to boost the sensitivity and precision of our quantum sensors for inertial sensing (gravity sensing in our case). We will build specialized systems that are not readily available in the market, namely: an ultra-high vacuum system, a precise laser stability method, and a high-coherence probe laser beam. We will then integrate these components into the experiment to create a complete CAI system. To the best of our knowledge, no previous experiment used our novel phase-stable system to construct a CAI system, which is envisioned to be highly sensitive due to the reduced internal noise. Such experiments have been conducted in different parts of the world but never in the State of Qatar. Along with the improvements we will introduce to this scheme, we expect to observe higher precision and stability, especially since the landscape and the smaller area size of the state of Qatar make it ideal for ground-based gravity mapping. The CAI system we will build in this project can support many quantum sensing technologies, such as gravimeters and gyroscopes. In fact, the CAI system we will build can eventually and potentially replace today's (classical) inertial sensing systems and tackle many problems humanity faces as they can precisely measure extremely small gravitational changes due to any mass change underground. This can drastically impact many applications, such as detecting natural resource depletion and oil and gas exploration.

Hamad Bin Khalifa University (HBKU)