By miniaturizing cold atom trapping with integrated photonics, researchers are making quantum technologies portable.
Their photonic chip system replaces traditional free-space optics, offering a path toward highly precise, deployable quantum sensors and computing tools.
Bringing Quantum Experiments to the Chip Level
Researchers at UC Santa Barbara are working to shrink cold atom quantum experiments from large laboratory setups to compact, chip-based systems. This advancement could revolutionize fields like precision sensing, timekeeping, quantum computing, and fundamental science.
“We’re at the tipping point,” said Daniel Blumenthal, a professor of electrical and computer engineering.
The Power of Cold Atoms
In a featured article for Optica Quantum, Blumenthal and his colleagues — graduate student Andrei Isichenko and postdoctoral researcher Nitesh Chauhan — highlight recent breakthroughs and future directions in trapping and cooling atoms. Their work aims to bring these powerful quantum technologies into portable devices, potentially small enough to fit in the palm of your hand.
Cold atoms are cooled to extremely low temperatures, below 1 millikelvin, where their motion slows, and quantum effects become dominant. This makes them highly sensitive to faint electromagnetic signals and fundamental particles, making them ideal for ultra-precise timekeeping, navigation, and “qubits” for quantum computing applications.
Challenges of Miniaturization
In order to capitalize on these properties, many researchers currently work with highly sensitive laboratory-scale atomic optical systems to confine, trap, and cool the atoms. Conventionally, these systems use free-space lasers and optics, generating beams that are guided, directed and manipulated by lenses, mirrors, and modulators. These optical systems are combined with magnetic coils and atoms in a vacuum to create cold atoms using the ubiquitous 3-dimensional magneto-optical trap (3D-MOT). The challenge that researchers face is how to replicate the laser and optics functions onto a small, durable device that could be deployed outside of the highly controlled environment of the lab, for applications such as gravitational sensing, precision timekeeping and metrology, and quantum computing.
A Breakthrough in Photonic Integration
The Optica Quantum review article covers recent and rapid advancements in the realm of miniaturizing complex cold-atom experiments via applications of compact optics and integrated photonics. The authors reference photonics achievements across a variety of sub-fields, ranging from telecommunications to sensors, and map the technology development to cold atom science.
“We created cold atoms with integrated photonics for the first time.”
“There’s been a lot of really great work miniaturizing beam delivery,” said Isichenko, “but it’s been done with components that are still considered free-space optics — smaller mirrors or smaller gratings — but you still couldn’t integrate multiple functionalities onto a chip.”
Enter the researchers’ photonic integrated 3D-MOT, a miniaturized version of equipment used widely in experiments to deliver beams of light to laser cool the atoms. Embedded into a low-loss silicon nitride waveguide integration platform, it’s the part of a photonic system that generates, routes, expands and manipulates all the beams necessary to trap and cool the atoms. The review article highlights the photonic integrated 3D-MOT — or “PICMOT” demonstrated by the UC Santa Barbara team as a major milestone for the field.
“With photonics, we can make lasers on chip, modulators on chip and now large-area grating emitters, which is what we use to get light on and off the chip,” Isichenko added.
Trapping Atoms with Precision
Of particular interest is the atomic cell, a vacuum chamber where the atoms are trapped and cooled. One feat the researchers accomplished was to route the input light from an optical fiber, which is less than the width of a hair, via waveguides to three grating emitters that generate three collimated free-space intersecting beams 3.5 mm wide. Each beam is reflected back on itself for a total of six intersecting beams that trap a million atoms from the vapor inside the cell and, in combination with magnetic fields, cool the atoms to a temperature of just 250 uK. The larger the beams the more atoms can be trapped into a cloud and interrogated, Blumenthal noted, and the more precise an instrument can be.
“We created cold atoms with integrated photonics for the first time,” said Blumenthal.
Expanding the Reach of Quantum Technology
The implications of the researchers’ innovations are far-reaching. With planned improvements to durability and functionality, future chip-scale MOT designs can take advantage of a menu of photonic components, including recent results with chip-scale lasers. This can be used to optimize technology for applications as diverse as measuring volcanic activity to the effects of sea level rise and glacier movement by sensing the gradient of gravity on and around the Earth.
Integration of the 3D-MOT can give quantum scientists and timekeepers new ways to send today’s earthbound instruments into space, conduct new fundamental science, and enable measurements not possible on Earth. Additionally, the devices could advance research projects by decreasing the time and effort spent establishing and fine tuning optical setups. They can also open the door to accessible quantum research projects for future physicists.
Reference: “Enabling photonic integrated 3D magneto-optical traps for quantum sciences and applications” by Daniel J. Blumenthal, Andrei Isichenko and Nitesh Chauhan, 24 December 2024, Optica Quantum.
DOI: 10.1364/OPTICAQ.532260
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