Someday, a hard drive could hold more bytes of information than there are stars in the observable universe.
And it may look like the diagram on this page: A crystal lattice of magnetic moments — also called spins — inside a newly created ceramic material. Something like it could end up as part of a quantum computer.
But today, Georgia Tech physicists are using such crystals to tinker with well-known quantum conundrums, such as 1) a particle can be in two states at the same time, and 2) particles, even when they’re miles apart, can be linked in a “spooky” way.
Martin Mourigal is a quantum ghostbuster and assistant professor in Georgia Tech’s School of Physics. Along with postdoctoral researcher Joseph Paddison and colleagues at Cambridge University in Britain, he experimented with electrons’ spins carried by dysprosium atoms (symbol Dy) organized on a special crystal lattice named “kagome,” after the Japanese basket weave pattern it strongly resembles.
The researchers tracked the spooky behavior of spins down to a temperature below −272.85 degrees Celsius — almost absolute zero Kelvin, which is −273.15 degrees Celsius. There, they found that slippery quantum properties in the new material with the chemical formula Dy3Mg2Sb3O14 produced straitlaced effects.
To the diagram: At every intersection of the black lines sits a Dy atom. These are not marked on the graph, and the blue and red dots stand for something else — an astounding discovery connected to the arrows at the intersections, which create the dots.
The arrows denote electron spin directions, and in any given triangle, no three spins can point to the inside or the outside at the same time. One arrow always must point in one direction and two in the opposing direction.
When any two arrows point inside a triangle, the triangle has a net positive spin, represented by a red dot. When any two arrows — or spins — point out, the triangle has a net negative spin, denoted by a blue dot.
“At nearly absolute zero, we expected a well-organized pattern for the spins — like in a (quantum physics) solid,” Mourigal said. “But to our great surprise, we found that spin directions remain frenzied like in a liquid.”
Another great surprise: Despite this, net spin values in the triangles aligned into a well-ordered, stable pattern of positives, or red dots, evenly interspersed with negatives, or blue ones.
“That’s like a solid in the quantum physics sense,” Mourigal said. “So, we’ve found a state of matter that behaves simultaneously like a liquid and like a solid because of the exotic yet concerted interaction between the spins.”
How could that contribute to a 1 quadrillion gigabyte hard drive? Each blue or red dot could represent one bit of information. And since each is on an atomic scale, a concise crystal could hold 1022, or many more. — Ben Brumfield