Scientists at the University of Chicago and their collaborators have developed a new kind of molecular qubit that could connect directly with today’s fiber-optic networks—a key step toward creating a “quantum internet.”
The breakthrough, published in Science, offers a way to make quantum technologies more practical, scalable, and compatible with existing telecommunications systems.
Qubits, or quantum bits, are the basic units of quantum technology.
Unlike regular bits, which can only be 0 or 1, qubits can exist in multiple states at once, allowing them to store and process vastly more information.
Molecular qubits are special because they can be chemically designed to have specific properties and are small enough to fit into a wide range of materials, from solid chips to biological systems.
They could be used not only for quantum communication and computing, but also as ultrasensitive sensors that measure magnetic fields, temperature, or pressure on the tiniest scales.
The new qubits developed by the UChicago team are made with erbium, a rare-earth element already used in many fiber-optic technologies.
Erbium is ideal for this purpose because it interacts strongly with both light and magnetic fields, acting as a bridge between them.
This allows information stored in the magnetic “spin” of the molecule to be accessed and transmitted by light—specifically, light at wavelengths already used in telecommunications.
“These molecules can act as a nanoscale bridge between the world of magnetism and the world of optics,” said Leah Weiss, a postdoctoral researcher at the University of Chicago’s Pritzker School of Molecular Engineering and one of the study’s first authors.
“That means we can encode information magnetically and read it using light through existing optical fiber networks.”
Using a combination of laser-based and microwave techniques, the team showed that their erbium-based qubits can operate at the same frequencies used by silicon photonics—the technology that underpins modern data transmission and computer chips.
This compatibility could make it easier to integrate molecular qubits into practical quantum devices, leading to networks that connect quantum computers over long distances or sensors that share information instantly and securely.
“By demonstrating the versatility of these erbium molecular qubits, we’re taking another step toward scalable quantum networks that can plug directly into today’s optical infrastructure,” said Prof. David Awschalom, senior author of the study. “These engineered qubits already have the qualities needed for building complex quantum systems.”
The project involved close collaboration between physicists and chemists from the University of Chicago, UC Berkeley, Argonne National Laboratory, and Lawrence Berkeley National Laboratory.
According to the researchers, the success of this partnership highlights how chemistry can be used to design quantum materials with precision at the molecular level.
“This study is just scratching the surface,” said UC Berkeley chemist Ryan Murphy.
“It shows that we can custom-build molecules to achieve the optical and magnetic properties needed for the next generation of quantum technologies.”
