Scientists say they have achieved quantum entanglement — a spooky state where the behavior of separate atoms is linked even if they are huge distances apart — for thousands of atoms.

Using just a single photon to initiate the process, physicists from MIT and the University of Belgrade say they've successfully achieved mutual entanglement of a record number of atoms, around 3,000.

Though a laboratory achievement for now, entanglement could be used to create more precise atomic clocks and more accurate GPS devices, they say, and advance quantum computing.

In entanglement, as physicists explain it, two or more particles are linked such that any change in one will simultaneously cause a change in the other, even if they are far apart, whether by thousands of miles or thousands of light years.

Both classical physics and quantum physics describe such a phenomenon, once famously put down by Albert Einstein, as "spooky action at a distance."

However, it has been proven that particles at the nanoscale do in fact behave differently that what is observed at larger scales.

Scientists have long been looking at ways of entangling not just pairs but large assemblages of atoms, which could lead to more accurate atomic clocks, which are based on oscillations occurring in a cloud of constrained atoms.

The more atoms that can be entangled, the more likely large numbers of them will oscillate together, improving the resulting clock accuracy.

That led the researchers to try and entangle as many atoms as possible.

Vladan Vuletic of MIT's Department of Physics, along with his research colleagues, successfully created mutual entanglement among 3,000 atoms using extremely weak laser light, using pulses containing a single photon.

"You can make the argument that a single photon cannot possibly change the state of 3,000 atoms, but this one photon does — it builds up correlations that you didn't have before," says Vuletic, lead author of a study published in the journal Nature.

The researchers say their work could lead to state-of-the art atomic clocks more accurate than anything built to date, using ever more complex entangled states than what they've already achieved.

"This particular [current] state can improve atomic clocks by a factor of two," Vuletic says. "We're striving toward making even more complicated states that can go further."

And he's not talking thousands, either.

"We could go to entangling a million atoms relatively straightforwardly," he says.

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