Physicists Entangle Two Macroscopic-Scale Objects

Entanglement — an intriguing phenomenon in which two distant objects can manifest correlations, even if they are far away from each other — has now been made a reality in macroscopic-scale objects.

An illustration of tiny drumheads prepared on silicon chips used in the experiment; the drumheads vibrate at a high ultrasound frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Image credit: Petja Hyttinen Olli Hanhirova, ARKH Architects / Aalto University.

In a paper published in the April 25, 2018 issue of the journal Nature, University of Chicago’s Professor Aashish Clerk and co-authors detail how they managed to entangle perhaps the largest items yet, at a whopping 20 microns across.

“Harnessing the mysterious property that Albert Einstein called ‘spooky action at a distance’ is a crucial step toward exploiting quantum quirks for technology such as new kinds of sensors or computers,” the physicists said.

“Entanglement is not just some academic curiosity; it’s also something you can harness as a basis for doing useful things with quantum mechanics,” Professor Clerk added.

Entangled states are typically extremely fragile — especially so when they involve large objects. So Professor Clerk and his colleague, Dr. Matt Woolley from the University of New South Wales, developed a theoretical proposal for how to keep the motion of large objects entangled.

Their approach involves involved coupling the objects to a specially designed circuit made out of a superconducting metal — a special material that can have zero electrical resistance, meaning that it conducts electricity perfectly.

This circuit acts to keep the two objects in the special entangled quantum state: when they are disturbed and threaten to fall out of alignment, the circuit nudges the two objects back into the entangled state.

Aalto University researcher Dr. Mika Sillanpää and his group put the idea to the test.

The physicists used a circuit to entangle the motion of two aluminum plates, each one vibrating like a tiny drumhead.

Not only did it work, but they were able to keep the plates entangled for times approaching an hour.

“The vibrating bodies are made to interact via a superconducting microwave circuit,” Dr. Sillanpää said.

“The electromagnetic fields in the circuit are used to absorb all thermal disturbances and to leave behind only the quantum mechanical vibrations.”

“In the future, we will attempt to teleport the mechanical vibrations,” added Dr. Caspar Ockeloen-Korppi, also from Aalto University.

“In quantum teleportation, properties of physical bodies can be transmitted across arbitrary distances using the channel of ‘spooky action at a distance’.”

“Looking towards the future, there’s a lot of interest in using mechanical objects in quantum regimes for applications,” Professor Clerk said.

“This includes powerful new kinds of sensors, with potential applications ranging from new ways to look inside the human body to even better methods to detect ripples of gravitational waves from faraway stars and black holes.”

“Such mechanical objects also could be a powerful way to integrate different systems to make up a quantum computer or quantum network.”

“Mechanical motion could be a kind of ‘bus’ for quantum information.”

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C.F. Ockeloen-Korppi et al. 2018. Stabilized entanglement of massive mechanical oscillators. Nature 556: 478-482; doi: 10.1038/s41586-018-0038-x