US physicists build quantum timekeeper that packs several atomic clocks

Researchers at the University of Colorado (UC) Boulder and the National Institute of Standards and Technology (NIST) have created a room-sized quantum timekeeper made up of multiple smaller atomic clocks, a press release said.

This might appear as a physicist’s equivalent of a timepiece connoisseur collecting the quantum equivalent of grandfather clocks. But the research team led by Adam Kaufman, a professor of physics at UC Boulder and a physicist at NIST, has a very simple logic for doing this: increasing the performance of the atomic clock using quantum entanglement.

“Optical clocks have become an important platform in many areas of quantum physics because they allow you to control individual atoms to such a high degree—both where those atoms are, and also what states they’re in,” said Kaufman in a press release.

But for all its advantages, quantum clocks have one major problem – the unexpected behavior of atoms.

How quantum entanglement helps

When two particles are entangled in the quantum world, they reveal information about the other and behave like a single atom instead of individual ones. If researchers know which quantum particles are entangled, it becomes easier to predict their behavior.

In another form, if researchers can get two atoms entangled in their quantum states, their behavior can be less erratic and much more predictable. In their recent work, Kaufman and his team created such entanglement in strontium atoms, resulting in their electrons moving away from the nuclei.

“It’s like a fluffy orbit,” Kaufman added. “This fluffiness means that if you bring two atoms close enough, the electrons can feel each other nearby, resulting in a strong interaction between them.” But that’s not all.

The entangled pair of electrons also tick faster together than if they were ticking on their own. ‘Ticking’ in atomic clocks is the jumping of electrons from a low energy state to a high energy one and then back to low energy again. This is much like the pendulum of an analog clock but occurs at the pace of a trillion times per second.

What did the researchers achieve?

Kaufman’s team created a new atomic clock by trapping a dozen strontium atoms in a lattice structure and squishing four different kinds of clocks into the same apparatus. This allowed the researchers to entangle groups of two, four, and eight atoms and, in effect, combine the rates of four ticking clocks into one.

Under these conditions, the ticking of entangled atoms displays much less uncertainty than a traditional optical atomic clock. “That means that it takes us less time to get to the same level of precision,” Kaufmann added. “What we’re able to do is divide the same length of time into smaller and smaller units, that acceleration could allow us to track time more precisely .”

This could help develop new quantum technologies that are sensitive enough to measure subtle environmental changes. Other applications could include multi-qubit gates needed for calculations in quantum computers.

The research findings were published in the journal Nature today.