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Sphere of Superfluid Helium Behaves Like Black Hole, Physicists Say

A team of physicists from the Universities of Vermont and Waterloo has discovered that a sphere of cold helium atoms follows a bizarre law of physics — called an entanglement area law — also observed in black holes. The discovery is reported March 13 in the online edition of the journal Nature Physics.

Entanglement across a spherical boundary: a container of superfluid helium-4 is bipartitioned into a sphere of helium atoms A (green) and its complement A- (blue). The entanglement between A and A- is dominated by an area law, scaling with area of the bounding surface. Image credit: C.M. Herdman et al, doi: 10.1038/nphys4075.

Entanglement across a spherical boundary: a container of superfluid helium-4 is bipartitioned into a sphere of helium atoms A (green) and its complement A (blue). The entanglement between A and A is dominated by an area law, scaling with area of the bounding surface. Image credit: C.M. Herdman et al, doi: 10.1038/nphys4075.

In the 1970s, famed theoretical physicists Stephen Hawking and Jacob Bekenstein discovered something strange about black holes.

They calculated that when matter falls into one of these bottomless holes in space, the amount of information it gobbles up — what physicists call its entropy — increases only as fast as its surface area increases, not its volume.

“We have found the same type of law is obeyed for quantum information in superfluid helium,” said Adrian Del Maestro, an assistant professor in the Department of Physics at the University of Vermont and corresponding author of the study.

To make their discovery, Dr. Del Maestro and co-authors first created an exact simulation of the physics of extremely cold helium-4 (isotope of the element helium) after it transforms from a gas into a form of matter called a superfluid.

“Below about two degrees Kelvin, helium-4 atoms — exhibiting the dual wave/particle nature that Max Planck and others discovered — become glopped together such that the individual atoms cannot be described independent from each other,” the researchers explained.

“Instead, they form a cooperative dance that the scientists call quantum entangled.”

Using two supercomputers, they explored the interactions of 64 helium atoms in a superfluid.

They found that the amount of entangled quantum information shared between two regions of a container — a sphere of the superfluid helium-4 partitioned off from the larger container — was determined by the surface area of the sphere and not its volume.

Like a holograph, it seems that a 3D volume of space is entirely encoded on its 2D surface. Just like a black hole.

This idea had been guessed at from a principle in physics called ‘locality’ but had never been observed before in an experiment.

By using a complete numerical simulation of all the attributes of helium-4, the team was — for the first time ever — able to demonstrate the existence of the entanglement area law in a real quantum liquid.

“Superfluid helium-4 could become an important resource — the fuel — for a new generation of quantum computers,” Dr. Del Maestro said.

“But to make use of its huge information processing potential, we have to understand more deeply how it works.”

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C.M. Herdman et al. Entanglement area law in superfluid 4He. Nature Physics, published online March 13, 2017; doi: 10.1038/nphys4075

This article is based on text provided by the University of Vermont.