First Quantum Entanglement Of Distant Objects Large Enough To See

Light coming from the right of the image passes a cloud of atoms whose spin is controlled by the magnetic field in which they sit, and entangles these atoms with an oscillating membrane on the left. Neils Bohr Institute

For the first time, scientists have succeeded in creating quantum entanglement where one side of the entanglement is large enough to see without a microscope. This represents a major step beyond the entanglement of subatomic particles (usually identical ones) that represented early achievements in this field.

Entanglement is one of the strangest and most intuition-defying aspects of quantum behavior, and it is not like the competition isn’t fierce. Entangled particles behave as a single entity where any changes made to one affect the others. Stranger still, changes can be transferred simultaneously, leading to the phenomenon being dubbed “spooky action at a distance” by Albert Einstein, who refused to believe it was real, despite being part of its discovery.

Early efforts at entanglement involved pairs of sub-atomic particles in the same room, and then eventually at greater and greater distances. Recently, however, more complex phenomena have been achieved, including the recent entanglement of trillions of atoms. We’ve also learned that entanglement occurs naturally, for example within stars and quasars billions of light-years away

Nature Physics, a team led by Professor Eugene Polzik of the University of Copenhagen, have reported entangling a vibrating silicon nitride membrane a millimeter across and a cloud of a billion atoms. As in previous experiments, Polzik put the atomic cloud in a magnetic field and used light passing the cloud to entangle the oscillator, but took the idea to a different scale.

“The bigger the objects, the further apart they are, the more disparate they are, the more interesting entanglement becomes from both fundamental and applied perspectives,” said Polzik in a statement. “With the new result, entanglement between very different objects has become possible."

The idea that quantum entanglement could make real ideas from science fiction, such as matter transmitters or ansibles, has been a major motivation for research on the topic. Nevertheless, we’re many advances away from either of them, even if they eventually prove possible.

On the other hand, Polzik is getting tantalizingly close to a useful application for his work.

Our most sensitive measuring devices are limited in their precision by the Heisenberg Uncertainty Principle and the intrinsic noise of the system. Entanglement cuts down this noise and gets around the Uncertainty Principle, raising the possibility that a larger version of Polzik’s entangled oscillator could enhance the sensitivity of gravitational wave detectors and other high-precision measuring devices. Although Laser Interferometer Gravitational-wave Observatories (LIGOs) have achieved some of the most important physics breakthroughs of recent years, major goals, such as the detection of continuous gravitational waves, elude them.

It’s not known whether this is because operators have yet to analyze data from the relevant parts of the sky or if the detectors simply lack the sensitivity required. In the latter case, coupling LIGO’s mirrors, instead of Polzik’s membranes, with an atomic cloud and using the cloud to suppress the mirrors’ noise might be the solution. Polzik is already working on an experiment hoping to demonstrate the viability of this approach.


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