The spin of the electron is nature’s perfect quantum bit, capable of extending the range of information storage beyond “one” or “zero.” Exploiting the electron’s spin degree of freedom (possible spin states) is a central goal of quantum information science.

Recent progress by Lawrence Berkeley National Laboratory (Berkeley Lab) researchers Joseph Orenstein, Yue Sun, Jie Yao, and Fanghao Meng has shown the potential of magnon wave packets – collective excitations of electron spins – to transport quantum information over substantial distances in a class of materials known as antiferromagnets. Their work upends conventional understanding about how such excitations propagate in antiferromagnets. The coming age of quantum technologies – computers, sensors, and other devices – depends on transmitting quantum information with fidelity, over distance.

With their discovery, reported in a paper published in Nature Physics, Orenstein and coworkers hope to have moved a step closer to these goals. Their research is part of broader efforts at Berkeley Lab to advance quantum information by working across the quantum research ecosystem, from theory to application, to fabricate and test quantum-based devices and develop software and algorithms.

Electron spins are responsible for magnetism in materials and can be thought of as tiny bar magnets. When neighboring spins are oriented in alternating directions, the result is antiferromagnetic order and the arrangement produces no net magnetization.

To understand how magnon wave packets move through an antiferromagnetic material, Orenstein’s group used pairs of laser pulses to perturb the antiferromagnetic order in one place while probing at another place, yielding snapshots of their propagation. These images revealed that magnon wave packets propagate in all directions, like ripples on a pond from a dropped pebble.