University of Waterloo quantum scientists make neutrons spin and grow
Saturday, November 26, 2022
WATERLOO — Dusan Sarenac’s experiments at the University of Waterloo are the stuff of science fiction — making subatomic particles spin on command and expand greatly in size.
Sarenac works with neutrons, which are found in the centre of atoms. You can lay more than 10,000 neutrons across a single strand of human hair.
For more than 15 years scientists tried to make neutrons spin. They call this angular momentum, a term for describing something that moves without really going anywhere.
Think of a child’s top. It spins very quickly, but stays in one place. Planets spin around the sun, and electrons spin around individual atoms. But those objects do not move beyond their clearly defined orbits.
The child’s toy, planets and electrons all have angular momentum.
Sarenac’s team wanted to make neutrons do the same thing because they have special properties that can be used by researchers — they are electrically neutral and can pass through materials that block light and X-rays.
His team of researchers at the Institute for Quantum Computing on the UW campus built six million microscopic structures that cover a square that is only a quarter of a centimetre in size.
The team then took their microscopic devices — called silicon-grating structures — to the nuclear reactor at the Oak Ridge Laboratory in Tennessee. They sent a beam of neutrons through the grating structures, and used a special camera to record what happened next.
After travelling 19 metres, the neutrons were not only spinning, but they had grown in size to 10 centimetres. After celebrating their discovery and publishing a paper, Sarenac is now free to talk about it.
“After going through our device, which gave them a special property, they actually reached around 10 centimetres, which was very astonishing on its own,” said Sarenac.
“So every one of these little neutrons that are usually 10,000 times smaller than a hair, even smaller than that, and we basically expanded them to 10 centimetres,” said Sarenac.
Spinning neutrons can be used to study and characterize materials that will be used in the next generation of supercomputers. Because they pass through materials that block light and X-rays and are electrically neutral, the spinning neutrons will tell scientists whether a new material can be used in a quantum simulator and later, a quantum computer.
“Light sees one thing, X-rays see one thing, electrons see another thing,” said Sarenac. “Neutrons are great for going through materials and looking at the magnetic structure of materials.”