by Amara Graps

Atom Interferometry Introduction

Interferometry. In our quantum technology landscape of superposition and entanglement, how nice it is to encounter a tool derived from classical optics from our formative physics years. No physics student can forget the experiment that discredited the aether drift theory. The “M” from Michelson has been a part of the acronyms of countless science instruments flying in space and deployed on the ground. 

GQI has a variety of resources to analyze the Quantum Technology Sensor sector, which is well-advanced across the Quantum Sensing Stack. See the Sensing Stack Framework in the Figure below. In GQI’s Quantum Sensing Outlook Report, the Report walks you through the operation principles of Atom Interferometry.

The principles are based on the wave character of light and the interference patterns generated by splitting and recombining a coherent beam. Interferometers are finely sensitive to variations in the light path length between the split and recombined beams. 

In quantum theory, matter also possesses a wave-like quality. The energy of an atom determines its de Broglie wavelength. In atom interferometry, the careful splitting and recombination of the path of an atom cloud in a gravity potential provide exceptional sensitivity to gravitational forces. After recombination of the atom cloud, due to one path having less energy and a longer de Broglie wavelength, atom interferometers can be used as a gravimeter or accelerometer. 

GQI’s Quantum Sensing Outlook Report highlights several appealing features about the cold atom interferometer:

  • Without requiring further external calibration, it can offer an absolute time measure when controlled by frequency stabilized lasers locked to appropriate time standard. 
  • The same basic system can be utilized to accomplish other sensing functions (time, rotation, magnetic fields, acceleration/gravity, etc.) by manipulating the laser control pulses with software. 
  • A small vacuum cell can withstand environmental disturbances and has no moving parts.

Abend et al., 2023 in Technology roadmap for cold-atoms based quantum inertial sensor in space provide additional education about cold atom interferometers. Their Table I lists the proposed cold atom-based space missions currently under study or operation. See the CARIOQA space mission, with its gravity field recovery, which has a performance goal of gradient sensitivity of 10-14 s-2 Hz-1/2. 

CARIOQA

The CARIOQA (Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry) mission is a European Union-funded project, which aims to improve Earth gravity measurements from space while advancing climate change science. CARIOQA’s Phase A kicked off  in January 2024. Water is one of the masses, with distribution changes in response to changes in the Earth’s gravity field. These gravity alterations should be detectable, which would enable scientists to monitor changes in ice sheets, groundwater, and other areas. In our climate change crisis, forecasting natural disasters like droughts and floods, and managing water supplies all depend on this knowledge.

The GQI Quantum Sensing Stack framework 

As for GQI’s Quantum Computing Stack, GQI has a Sensing Stack framework, as well. 

Figure. GQI’s Quantum Sensing Stack Framework (*).

We’ll dive deeper into Quantum Technology’s Sensor subfield, Atom Interferometry, next time. 

(*) GQI’s Quantum Sensors State of Play presentation is a 33-slide, introduction and walk-through, to bring you up to date on current trends. If you are interested to learn more, please don’t hesitate to contact info@global-qi.com

September 30, 2024