Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences
A portable magneto-optical trap with prospects for atom interferometry in civil engineering
Andrew Hinton, Marisa Perea-Ortiz, Jonathan Winch, J. Briggs, Suzanna Freer, D. Moustoukas, S. Powell-Gill, C. Squire, Andrew Lamb, Clemens Rammeloo, Ben Stray, Georgios Voulazeris, Lingxiao Zhu, Ajeet Kumar Kaushik, Yu-Hung Lien, Alexander Niggebaum, Anthony Rodgers, Artur Stabrawa, Daniel Boddice, Simon R. Plant, George Tuckwell, Kai Bongs, Nicole Metje, Michael Holynski
The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 10 7 atoms within a system package of 20 l and 10 kg, consuming 80 W of power. This article is part of the themed issue ‘Quantum technology for the 21st century’.
The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 10 7 atoms within a system package of 20 l and 10 kg, consuming 80 W of power. This article is part of the themed issue ‘Quantum technology for the 21st century’.
Borehole gravity sensing can be used in a number of applications to measure features around a well, including rock-type change mapping and determination of reservoir porosity. Quantum technology gravity sensors, based on atom interferometry, have the ability to offer increased survey speeds and reduced need for calibration. While surface sensors have been demonstrated in real world environments, significant improvements in robustness and reductions to radial size, weight, and power consumption are required for such devices to be deployed in boreholes. To realise the first step towards the deployment of cold atom-based sensors down boreholes, we demonstrate a borehole-deployable magneto-optical trap, the core package of many cold atom-based systems. The enclosure containing the magneto-optical trap itself had an outer radius of (60 ± 0.1) mm at its widest point and a length of (890 ± 5) mm. This system was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep borehole, to simulate how in-borehole gravity surveys are performed. During the survey, the system generated, on average, clouds of (3.0 ± 0.1) × 105 87Rb atoms with the standard deviation in atom number across the survey observed to be as low as 8.9 × 104.
Borehole gravity sensing can be used in a number of applications to measure features around a well including rock-type change mapping and determination of reservoir porosity. Quantum technology gravity sensors based on atom interferometry have the ability to offer increased survey speeds and reduced need for calibration. While surface sensors have been demonstrated in real world environments, significant improvements in robustness and reductions to radial size, weight, and power consumption are required for such devices to be deployed in boreholes. To realise the first step towards the deployment of cold atom-based sensors down boreholes, we demonstrate a borehole-deployable magneto-optical trap, the core package of many cold atom-based systems. The enclosure containing the magneto-optical trap itself had an outer radius of (60±0.1) mm at its widest point and a length of (890±5) mm. This system was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep borehole, to simulate an in-borehole gravity surveys are performed. During the survey the system generated on average clouds of (3.0 ±0.1)×10587Rb atoms with the standard deviation in atom number across the survey observed to be as low as 9×104.
With over 20 years of development, atomic interferometry gravimeters have distinguished themselves in gravity measurements by their high precision and sensitivity. To cater to the demands of field absolute gravity measurements for marine and aerial gravity field measurements, resource exploration, inertial navigation, and positioning, the miniaturization, mobility, and engineering of atomic interferometry gravimeters have become crucial areas of development. On this basis, this article elucidates the principles of atomic interferometry gravimeters, encompassing various laser cooling techniques, magneto-optical traps, and Raman light interference. As a matter of fact, it provides an overview of the principles and achieved precision benchmarks of portable, vehicular, airborne, and shipborne atomic interferometry gravimeters. Additionally, it analyzes the experimental content and results of maritime, terrestrial, and aerial experiments based on portable atomic interferometry gravimeters. The limitations of portable atomic interferometry gravimeters are discussed, along with an exploration of their application prospects. Overall, these results shed light on guiding further exploration of mobile atom interferometry gravity.
The extraordinary performance offered by cold atom-based clocks and sensors has the opportunity to profoundly affect a range of applications, for example in gravity surveys, enabling long term monitoring applications through low drift measurements. While ground-based devices are already starting to enter the commercial market, significant improvements in robustness and reductions to size, weight, and power are required for such devices to be deployed by Unstaffed Aerial Vehicle systems (UAV). In this article, we realise the first step towards the deployment of cold atom based clocks and sensors on UAV’s by demonstrating an UAV portable magneto-optical trap system, the core package of cold atom based systems. This system is able to generate clouds of 2.1±0.2×107 atoms, in a package of 370 mm × 350 mm × 100 mm, weighing 6.56 kg, consuming 80 W of power.
Gravity sensing is a valuable technique used for several applications, including fundamental physics, civil engineering, metrology, geology, and resource exploration. While classical gravimeters have proven useful, they face limitations, such as mechanical wear on the test masses, resulting in drift, and limited measurement speeds, hindering their use for long-term monitoring, as well as the need to average out microseismic vibrations, limiting their speed of data acquisition. Emerging sensors based on atom interferometry for gravity measurements could offer promising solutions to these limitations, and are currently advancing towards portable devices for real-world applications. This article provides a brief state-of-the-art review of portable atom interferometry-based quantum sensors and provides a perspective on routes towards improved sensors.
A light-pulse atom interferometer for inertial sensing applications such as gravimetry is being commissioned, where the prototype has a target relative precision (σ g /g) of one part per million to enable geophysics applications, which is three orders of magnitude less sensitive than commercial optical gravimeters, but with the potential to exceed these. As part of this, a rubidium-85 magneto-optical trap was upgraded using optical amplification and fibre optics to capture an atom population number of O(10 8 ) and sub-Doppler cooling techniques have been used to reach ultracold temperatures of 20 μK. Several interferometer subsystems have been developed, including extensive optical systems featuring a high-specification optical modulator and laser-induced fluorescence detection. Preliminary investigations into the coherent manipulation of atomic states have been implemented and the resonance peak of a stimulated Raman transition has been observed.