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On the Atomic Highway, Researchers Help Atoms Stay in Their Lane

Blue light traveling along fiber optic cables
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As technology rapidly evolves, the need for faster, more precise position, navigation and timing (PNT) sensors is critical. One possibility lies with quantum science and technology. Trapping alkaline-earth elements, such as strontium, along photonic circuits could offer new insights and developments for a wide range of PNT quantum devices.

New research from University of California San Diego Assistant Professor of Physics Julio Barreiro and graduate students Grady Kestler and Khang Ton lays the groundwork by successfully trapping strontium atoms around a tapered optical fiber. The results of this work appear in PRX Quantum.

One of the limitations of GPS navigation is that it relies on a satellite signal, which may be unavailable. In those instances, travelers need item like maps, accelerometers, rotation sensors and gyroscopes to reach their destinations. The next generation of navigation without GPS belongs to the second quantum revolution, where improvements are on the horizon with technologies using atoms trapped on photonic chips.

The first step in developing this technology was to hold the atoms along light wires, or “highways” that keep the atoms in their lane. To do this, atoms must be slowed down considerably — achieved by laser cooling them to 1 microKelvin (one millionth of a degree above absolute zero). The slowed atoms were placed in close proximity to an optical fiber (the “highway”), which was tapered to be thinner than the wavelength of the light used on it — roughly a 200 nm fiber with 400 nm of light. This meant that when light passed through the fiber, some of it escaped in an evanescent field and trapped the strontium atoms.

With the foundation in place, the next step for Barreiro’s team in the quest for a new generation of rotation sensors is to bind the atoms to a photonic ring as a kind of roundabout. Because a ring has no end, light and atoms can move continuously, providing the ability to do unique rotation measurements with the atoms that are held and made to spin in both directions.

Trapping the atoms on photonic chips may also lead to novel quantum technologies. Currently, electronic circuits are used for sensors, but in the future, it may be atomtronic circuits, where atoms move along photonic pathways in more flexible configurations. The results from Barreiro’s research lay crucial groundwork, showing that it is possible to build a wire along which atoms can travel.

This research also has bearing on atomic clocks — used for international timekeeping, communications satellites and other kinds of research — and even in the fundamental physics of how individual atoms interact with a crystal.

“It’s really thrilling to be at the forefront of a new quantum technology,” stated Barreiro.

Funding provided by the Office of Naval (N00014-20-1-2513 and N00014-20-1-2693) and the National Science Foundation (PHY-2012068). This research was supported, in part, through the use of the University of Delaware’s HPC Caviness and DARWIN computing systems.

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