Qubits put a new spin on magnetism: boosting quantum computer applications – Phys.org

Research using a quantum computer as a physical platform for quantum experiments has found a way to design and characterize custom magnetic objects using quantum bits, or qubits. This opens up a new approach to developing novel materials and robust quantum computing.

“With the help of quantum annealing, we demonstrated a new way to model magnetic states,” said Alejandro Lopez-Bezanilla, a virtual experimenter in the Theoretical Division at Los Alamos National Laboratory. Lopez-Bezanilla is the corresponding author of an article on research in Scientists progress.

“We have shown that a magnetic quasicrystal lattice can host states that go beyond the zero and one-bit states of classical information technology,” Lopez-Bezanilla said. “By applying a magnetic field to a finite set of spins, we can transform the magnetic landscape of a quasi-crystalline object.”

“A quasicrystal is a structure composed by the repetition of certain basic shapes following different rules from those of regular crystals,” he said.

For this work with Cristiano Nisoli, a theoretical physicist also at Los Alamos, a D-Wave quantum annealing computer served as a platform for conducting real physical experiments on quasicrystals, rather than modeling them. This approach “lets matter talk to you,” Lopez-Bezanilla said, “because instead of running computer codes, we go straight to the quantum platform and define all physical interactions at will.”

The ups and downs of qubits

Lopez-Bezanilla selected 201 qubits on the D-Wave computer and coupled them together to reproduce the shape of a Penrose quasicrystal.

Since Roger Penrose in the 1970s designed the aperiodic structures that bear his name, no one had rotated each of their nodes to observe their behavior under the action of a magnetic field.

“I connected the qubits so that they all together replicate the geometry of one of its quasicrystals, the so-called P3,” Lopez-Bezanilla said. “To my surprise, I observed that applying specific external magnetic fields to the structure caused some qubits to exhibit up and down orientations with the same probability, leading to the quasicrystal P3 at adopt a rich variety of magnetic forms.”

Manipulating the force of interaction between qubits and qubits with the external field causes the quasicrystals to settle into different magnetic arrangements, offering the prospect of encoding more than one bit of information into a single object.

Some of these configurations do not present any precise order of the orientation of the qubits.

“That may work in our favor,” Lopez-Bezanilla said, “because they could potentially host a quantum quasiparticle of interest for information science.” A spin quasiparticle is able to carry information insensitive to external noise.

A quasiparticle is a convenient way to describe the collective behavior of a group of basic elements. Properties such as mass and charge can be attributed to multiple spins moving as one.