Researchers at the University of Colorado Boulder have developed a quantum navigation instrument that interprets acceleration akin to how a fingerprint scanner identifies thumbprints.
Employing atoms cooled to merely billionths of a degree beyond absolute zero, their innovative interferometer can concurrently gauge motion in three dimensions—something many professionals believed to be unachievable. This advancement could transform the navigation capabilities of submarines, spacecraft, and self-driving vehicles when GPS signals are unavailable or fail to operate.
In contrast to conventional accelerometers that monitor movement along one axis, this quantum device acquires a comprehensive understanding of motion in our three-dimensional reality. The implications extend well beyond navigation, potentially providing fresh tools for detecting gravitational waves, exploring essential physics, and even hunting for dark matter.
The Atomic Motion Detector
“Conventional atom interferometers can only gauge acceleration in one dimension, but we exist in a three-dimensional environment,” states Kendall Mehling, a graduate student in physics at CU Boulder and co-author of the paper published in Science Advances. “To determine my direction and track my past trajectory, I must monitor my acceleration in all three dimensions.”
The instrument operates by forming what researchers refer to as a “matter-wave pond” through a Bose-Einstein Condensate—an unusual state of matter that earned CU Boulder physicists Carl Wieman and Eric Cornell a Nobel Prize in 2001. In this quantum space, individual atoms exist in ethereal superpositions, occupying multiple locations simultaneously.
Here’s where it becomes truly extraordinary: when the atoms divide and merge, they generate intricate interference patterns that act as exclusive signatures for various types of motion. Consider it as each acceleration vector leaving its unique thumbprint in the quantum realm.
Decoding Quantum Fingerprints
What distinguishes this system is its advanced readout mechanism. Traditional interferometers create straightforward oscillating signals, but this quantum instrument produces what the researchers label a 49-channel output—essentially a 7×7 matrix of momentum measurements that generates distinct patterns for different acceleration vectors.
“We can decode that fingerprint and extract the acceleration experienced by the atoms,” remarks Murray Holland, a physics professor and JILA fellow who directed the research team.
The team showcased two different types of measurements: Bloch oscillations that monitor motion over time and Michelson interferometry that captures instantaneous acceleration snapshots. In one trial, they successfully assessed applied accelerations of 2g (twice the force of Earth’s gravity) across two axes simultaneously, achieving impressive accuracy.
Machine Learning Meets Quantum Physics
Creating this device involved tackling an immensely intricate engineering challenge. The team employs six laser beams, each finer than a human hair, to manipulate tens of thousands of rubidium atoms with remarkable precision. However, there’s a twist—they couldn’t tackle this challenge using conventional trial-and-error methods.
Instead, they leveraged artificial intelligence. The researchers trained machine learning algorithms to orchestrate the complex laser control sequences necessary to effectively split and combine atoms. This computational method allowed them to unearth control protocols that human intuition might have missed.
“For its nature, the current experimental setup is incredibly compact. Despite having 18 laser beams traversing the vacuum chamber housing our atom cloud, the entire experiment is compact enough that we could potentially deploy it in the field one day,” observes Catie LeDesma, a postdoctoral researcher on the team.
Beyond Traditional Navigation
The quantum method provides several benefits over standard accelerometers. Most crucially, atoms do not age or deteriorate like mechanical parts do.
“If you leave a classical sensor in different environments for extended periods, it will age and deteriorate,” Mehling emphasizes. “The springs in your clock will deform and alter. Atoms remain unchanged.”
At present, the device measures accelerations thousands of times smaller than Earth’s gravity—not yet comparable with existing technologies. However, the researchers envision substantial potential for enhancement. They anticipate that with prolonged measurement durations and improved engineering, sensitivity could reach levels relevant to technology.
More intriguingly, the system provides unparalleled programmability. Unlike hardware-based sensors designed for singular functions, this quantum device can be modified through software to work as an accelerometer, gyroscope, or gravity gradiometer whenever needed.
The Bayesian Advantage
Perhaps most notably, the team devised innovative data analysis techniques using Bayesian statistics to extract multiple parameters from single measurements. Traditional interferometers need numerous repeated experiments to accumulate interference fringes, but this quantum system can ascertain vector accelerations from individual snapshots.