Sandia Lab Guides Atoms with Minimal Power for Quantum
Sandia National Laboratories scientists have trapped cesium atoms on a 420-nanometer fiber using only 5 milliwatts of power, a key step toward chip-scale
Scientists at Sandia National Laboratories have guided atoms along an optical fiber using a fraction of the power previously required. Their experiment trapped cesium atoms on a fiber just 420 nanometers in diameter with only 5 milliwatts of optical power. The team also measured atomic coherence with a mere 150 nanowatts, mimicking the function of an atom interferometer.
According to a study published in AVS Quantum Science, this power level is roughly one-sixth to one-fourth of what earlier methods needed. Researcher Jongmin Lee stated the work shows a clear path toward chip-scale quantum inertial sensing. The ultimate goal is to build a rugged, low-power atom interferometer small enough to fit on a photonic integrated circuit. Such a device could provide precise navigation for military vehicles when GPS signals are jammed or unavailable.
The Need for Quantum Navigation
Jamming satellite navigation is straightforward: overwhelm receivers with electromagnetic noise. Aircraft then rely on onboard sensors, but these drift over time. Quantum sensors, which exploit quantum mechanics, offer a potential solution with far greater accuracy. An atomic clock is one familiar example. A quantum inertial sensor could keep a vehicle on course much longer during GPS outages.
Lee's guided atom interferometer concept offers a key advantage over alternative free-space designs. Free-space devices release ultracold atoms and measure their fall, but vibrations can cause lasers to lose sight of them. The guided approach, likened to marbles in a pipe, keeps atoms contained and within constant laser view. This makes it potentially resilient to turbulence and jolts.
Overcoming the Heat Challenge
A major hurdle has been heat. Lasers create the light halos that trap atoms, but they also generate heat. On ultrathin components, this heat can build rapidly and destroy the waveguide. Past designs forced a trade-off: fragile suspended waveguides that load atoms well but overheat, or sturdy mounted ones that handle heat but load atoms poorly.
The Sandia team developed a new membrane-waveguide design that balances both needs. It is anchored at each end by small silicon pins. These pins act as heat sinks, drawing heat away from the lasers in a vacuum. Lee explained that both efficient heat dissipation and atom loading are critical, and this platform addresses both.
Experimental Results and Future Work
The team's nanofiber experiments serve as a testbed for the principles. The reported power requirements for trapping and measurement are detailed below.
| Measurement Type | Optical Power Used |
|---|---|
| Atom Trapping | 5 milliwatts |
| Coherence Measurement | 150 nanowatts |
These results were achieved with a fiber 200 times thinner than a human hair. While nanofibers are convenient for research, they are impractical for real-world use. The future lies in the membrane-waveguide integrated onto a chip.
Lee outlined the next steps. The team will use laser cooling to create a cloud of slow-moving atoms. These atoms will drift into a hole in the membrane or a gap between silicon needles. The membrane-waveguide will then guide them using the same halo-of-light principle. The researcher said their work demonstrates trapping and coherence measurement while minimizing in-vacuum heat loads. This integration of cooling, trapping, and guiding into a single workflow is now underway.
