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Move over, lasers: Scientists can now create holograms using neutrons

Credit: E. Edwards/JQI

For the first time, a team including scientists from the National Institute of Standards and Technology (NIST) and JQI have used neutron beams to create holograms of large solid objects, revealing their interior details in ways that ordinary holograms do not.

Holograms—flat images that look like three-dimensional objects—owe their striking look to interfering waves. Both matter and light behave like waves at the smallest scales, and just like water waves traveling on the surface of the pond, waves of matter or light can combine to create information-rich interference patterns.

Illuminating an object with a laser can create an optical hologram. But instead of merely photographing the light reflected from the object, a hologram records how the reflected light waves interfere with each other. The resulting patterns, based on the waves’ phase differences, or relative positions of their peaks and valleys, contain far more information about an object’s appearance than a simple photo. Generally, though, they don’t reveal much about its interior.

It’s the interior neutron scientists explore. Neutrons are great at penetrating metals and many other solid things, making neutron beams useful for scientists who create a new substance and want to investigate its properties. But neutrons have limitations, too. Neutron beams typically probe average properties—fine for objects with repeating structures like a crystal, but not as good for spotting fine-grained details.

But what if we could have the best of both worlds? New research has found a way.

Previous work performed at the NIST Center for Neutron Research (NCNR) involved shooting neutrons through a cylinder of aluminum that had a tiny “spiral staircase” carved into one of its circular faces. The cylinder’s shape imparted a twist to the whole passing beam, but the beam’s individual neutrons also collected individual twists depending on the section of the cylinder that they passed through: the thicker the section, the greater the twist. Researchers realized this was the information needed to create holograms of objects’ innards, and the new paper details their method.

The discovery won’t change anything about interstellar chess games, but it adds to the palette of techniques scientists have to explore solid materials. The team has shown that all it takes is a beam of neutrons and an interferometer—a detector that measures interference patterns—to create direct visual representations of an object and reveal details about specific points within it.

"Other techniques measure small features as well, only they are limited to measuring surface properties," says team member Michael Huber of NIST’s Physical Measurement Laboratory. "This might be a more prudent technique for measuring small, 10-micron size structures and buried interfaces inside the bulk of the material."

The research was a multi-institutional collaboration that included scientists from NIST and JQI, as well as North Carolina State University and Canada’s University of Waterloo.

Story by Chad Boutin. The original story, along with several animations, was posted at NIST's news site. 

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