Physicists at the university of Colorado Boulder have unveiled a groundbreaking device capable of measuring acceleration in three dimensions using a cloud of supercooled atoms, a feat previously deemed unattainable by many in the scientific community.

This innovative atom “interferometer” holds the potential to revolutionize navigation systems for various vehicles, including submarines, spacecraft, and automobiles, offering enhanced precision and reliability.

According to Kendall Mehling,a graduate student in the Department of Physics at CU Boulder and co-author of the study,”traditional atom interferometers can only measure acceleration in a single dimension,but we live within a three-dimensional world. To know where I’m going, and to know where I’ve been, I need to track my acceleration in all three dimensions.”

The findings were published in the journal Science Advances under the title “Vector atom accelerometry in an optical lattice.” The research team also included Catie LeDesma, a postdoctoral researcher in physics, and Murray Holland, professor of physics and fellow of JILA, a joint research institute between CU Boulder and the National Institute of Standards and Technology (NIST).

In 2023, NASA awarded the CU Boulder researchers a $5.5 million grant through the agency’s Quantum Pathways institute to further develop this promising sensor technology.

The device utilizes six lasers,each thinner than a human hair,to immobilize a cloud containing tens of thousands of rubidium atoms. Artificial intelligence algorithms than manipulate these lasers in intricate patterns, enabling the team to monitor the atoms’ response to minute accelerations.

While current vehicles rely on GPS and conventional electronic accelerometers for tracking acceleration, the quantum device is still in its early stages. However, the researchers believe that atom-based navigation technology holds significant promise for the future.

The Advantage of Atoms

“If you leave a classical sensor out in different environments for years, it will age and decay,” said Mehling. “The springs in your clock will change and warp. Atoms don’t age.”

“To know where I’m going, and to know where I’ve been, I need to track my acceleration in all three dimensions.”

How it Works: Atomic Interferometry

Interferometers have a long history,with applications ranging from optical fiber communication to the detection of gravitational waves. The core principle involves splitting a wave or beam, sending the resulting parts along separate paths, and then recombining them. Differences in the paths alter the way the beams interfere with each other, revealing details about the forces or fields experienced along the way.

In laser interferometry, a laser beam is split into two identical beams that traverse different paths before being recombined. Any variations in the paths, such as those caused by gravity, will cause the beams to interfere with each other. The interference pattern provides valuable measurements.

The CU Boulder team has achieved a similar result using atoms rather of light.

The device,currently the size of an air hockey table,begins by cooling rubidium atoms to temperatures near absolute zero. At these temperatures, the atoms enter a Bose-Einstein Condensate (BEC), a unique quantum state of matter. Carl Wieman and Eric Cornell were awarded the Nobel Prize in 2001 for thier creation of the first BEC.

Next, laser light is used to manipulate the atoms, creating a superposition where each atom exists in two places together. These “ghost” atoms then travel along separate paths. (In this experiment, lasers are used to induce acceleration in the atoms.)

“Our Bose-einstein Condensate is a matter-wave pond made of atoms, and we throw stones made of little packets of light into the pond, sending ripples both left and right,” Holland explained. “Once the ripples have spread out,we reflect them and bring them back together where they interfere.”

When the atoms recombine, they create a unique interference pattern, similar to a thumbprint on glass.

“We can decode that fingerprint and extract the acceleration that the atoms experienced,” holland said.

AI Streamlines the Process

The device took the team nearly three years to construct.

“for what it is, the current experimental device is incredibly compact. Even though we have 18 laser beams passing through the vacuum system that contains our atom cloud, the entire experiment is small enough that we could deploy in the field one day,” LeDesma noted.

Machine learning plays a crucial role in the device’s operation. Splitting and recombining the rubidium atoms requires precise adjustments to the lasers. The team trained a computer program to plan these adjustments in advance, streamlining the process.

The device can currently measure accelerations much smaller than the force of Earth’s gravity, but the team aims to substantially improve its performance in the coming years.

“We’re not exactly sure of all the possible ramifications of this research, as it opens up a door,” Holland concluded.