Laser ‘egg carton’ traps giant atoms

U. MICHIGAN (US) — With an “egg carton” of laser light, physicists can trap giant Rydberg atoms with up to 90 percent efficiency.

The achievement could advance computing and terahertz imaging and detection devices that could be used in airport scanners or surveillance equipment, among other applications.

Highly excited Rydberg atoms can be 1,000 times larger than their ground state counterparts. Nearly ionized, they cling to faraway electrons almost beyond their reach. Trapping them efficiently is an important step in realizing their potential, researchers say.

In previous Rydberg atom traps, atoms came to rest at the top of the peaks of the laser light lattice, and tended to escape. University of Michigan researchers solved this problem by quickly flipping the lattice, trapping the giant Rydberg atoms in the wells, like eggs in a carton. (Credit: Sarah Anderson)


“Our optical lattice is made from a pair of counter-propagating laser beams and forms a series of wells that can trap the atoms, similar to how an egg carton holds eggs,” says Georg Raithel, professor of physics at the University of Michigan and co-author of a new study published in the journal Physical Review Letters.

Researchers developed a unique way to solve a problem that had been limiting trapping efficiency to single digit percentages. For Rydberg atoms to be trapped, they first have to be cooled to slow them down. The laser cooling process that accomplishes that tends to leave the atoms at the peaks of what the researchers call the “lattice hills.” But the atoms didn’t often stay there.

“To overcome this obstacle, we implemented a method to rapidly invert the lattice after the Rydberg atoms are created at the tops of the hills,” says co-author Sarah Anderson, a physics doctoral student.

“We apply the lattice inversion before the atoms have time to move away, and they therefore quickly find themselves in the bottoms of the lattice wells, where they are trapped.”

There is plenty of technological room left to reach 100 percent trapping efficiency, which is necessary for advanced applications, Raithel says.

Rydberg atoms are candidates to implement gates in future quantum computers that have the potential to solve problems too complicated for conventional computers.

The National Science Foundation and the Department of Energy funded the work.

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