Cold-Atom Source Brings Portable Quantum Devices Closer to Reality

A high-flux and compact cold-atom source with low power consumption developed by an Oxford University-led research group is poised to enable devices such as space-based atomic clocks, improving quantum applications for communication and navigation. The research is a step toward portable quantum devices.

“Compact atomic clocks that can be deployed more widely, including in space, provide resilience in communications networks because local clocks can maintain accurate timekeeping even if there is a network disruption,” said research team leader Christopher Foot of Oxford University. Quantum technologies based on laser-cooled atoms are already used for timekeeping on a national level, Foot said.

The researchers’ device is suitable for a wide range of cold-atom technologies. Foot said the group took a design created for research and made it compact. “In addition to timekeeping applications, compact cold-atom devices can also be used for instruments for gravity mapping, inertial navigation, and communications, and to study physical phenomena in research applications such as dark matter and gravitational waves,” Foot said.

Researchers designed a cold-atom source that uses four mirrors arranged like a pyramid and placed in a way that allows them to slide past each other like the petals of a flower. This creates an adjustable hole at the top of the pyramid through which the cold atoms are pushed out. This image shows a rendering of the device. Courtesy of Christopher Foot, Oxford University.

The design additionally features a pyramid-like arrangement of mirrors that influences the laser cooling mechanism. By exerting a force that slows down the motion of atoms, laser light can be used to cool atoms to extremely low temperatures. The process can be used to create a cold-atom source that generates a beam of laser-cooled atoms that are directed toward a region where the actual precision measurements (for timekeeping or the detection of gravitational waves) are performed.

Where laser cooling typically requires a complicated arrangement of mirrors to shine light onto atoms in a vacuum from all directions, the researchers said, their four-mirror, pyramid-like architecture allows the individual mirrors to slide past each other to create a hole at the top of the pyramid. The cold atoms are pushed through this hole, the size of which can be adjusted to optimize the flow of cold atoms for different applications.

The pyramid arrangement also reflects the light from a single incoming laser beam that enters the vacuum chamber through a single viewport, which the researchers said greatly simplifies the optics. The mirrors themselves were created by polishing metal to which the researchers then applied a dielectric coating.

To test the cold-atom source design, the researchers themselves constructed laboratory equipment to fully characterize the flux of atoms emitted through a hole at the pyramid’s apex.

“We demonstrated an exceptionally high flux of rubidium atoms,” Foot said. “Most cold-atom devices take measurements that improve with the number of atoms used. Sources with a higher flux can thus be used to improve measurement accuracy, boost the signal-to-noise ratio, or help achieve larger measurement bandwidths.”

The researchers report that the new cold-atom source is suitable for commercial applications. Because the source features only a small number of components and assembly steps, the team said scale-up potential would be straightforward.

The research was published in Optics Express (www.doi.org/10.1364/OE.423662).