In an article featured on the cover of this month’s Nature Reviews Materials, researchers at the University of Chicago, Argonne National Laboratory, and institutions in Japan, Korea and Hungary provide a blueprint for a class of materials that is quickly emerging as an important player in quantum science: crystals with defects.
The defects — irregularities deliberately embedded in the crystal’s structure — act like a trap for quantum particles. In their most fundamental form, these systems are known as qubits, the basic unit of quantum information.
The research team’s article in Nature Reviews Materials is one among several in an issue devoted entirely to the development of quantum systems.
“That Nature Reviews has focused an entire issue on the topic of qubit materials recognizes the prominence of this area of research,” said the article’s lead author David Awschalom, Argonne senior scientist, the University of Chicago Liew Family professor in molecular engineering and physics, and director of the Chicago Quantum Exchange. “We’re moving quantum science into the realm of usable, scalable devices. Developing quantum materials is foundational to that effort.”
A mashup of “quantum” and “bit,” the qubit corresponds to the traditional computing bit. Its physical realization can take on a variety of forms: It might be a lab-made molecule. Or it could be an electron traveling in a specialized superconducting circuit.
It could also be a particle of light trapped in a defect deep inside a fleck of diamond. This defect-in-a-crystal family of materials is the focus of the Awschalom team’s study, and they go by a fancy name: solid-state spin qubits. (“Spin” refers to a quantum property of an electron that scientists manipulate to process information. Solid state materials comprise insulators or semiconductors, such as diamond or silicon.)
“One advantage of a semiconductor qubit is that you can potentially leverage many of the solid-state technologies that are readily available from the semiconductor industry: integrated devices and circuits and the nanofabrication and processing that comes with solid-state systems,” Awschalom said.
Researchers engineer qubits based on how they will be used, whether in computing, communication or sensing, opening powerful new ways of processing information. Quantum sensors are expected to operate with many times the resolution of today’s sensors, enabling the study of human cells at the molecular level. Quantum communication networks promise to enable the transmission of hackerproof messages. And quantum computers will be able to rapidly game out complex simulations such as those used in the pharmaceutical industry, enabling faster drug delivery, for instance.
The development of practical qubits is key to a quantum future. In the Awschalom team’s handbook on solid-state spin qubit materials, researchers lay out their properties, engineering considerations and potential applications.