Scientists at the University of Chicago and partner institutions have demonstrated a new type of molecular qubit that operates at standard telecommunications wavelengths. The breakthrough could enable quantum networks to run over today’s fiber infrastructure. 

The research, published in Science, introduces an engineered organo-erbium molecule with tightly defined optical and spin transitions that can be addressed with telecom frequency light.

The result is a high-resolution spin-photon interface on a molecular platform, enabling magnetic quantum states to be accessed with optical signals compatible with silicon photonics and existing fiber-optic systems. The researchers say this hybrid capability could provide a building block for scalable quantum networking architectures and new classes of integrated quantum devices.

Molecular qubits are chemically designed molecules that exhibit quantum properties. Because they can be tailored at the atomic level and embedded in complex environments, they are being explored for quantum sensing, communication, and computation. The erbium-based molecules in the new study were engineered to combine two key traits: strong magnetic interactions linked to electronic spin states, and optical transitions that fall squarely within telecom bands used in long-haul fiber networks.

“These molecules can act as a nanoscale bridge between the world of magnetism and the world of optics,” said Leah Weiss, postdoctoral scholar at the UChicago Pritzker School of Molecular Engineering and co-first author. 

The team used optical spectroscopy and microwave techniques to show that the spin states can be polarized, addressed, and read out using telecom-frequency light with megahertz-scale resolution.

Such dual control could help bridge spin-based quantum processors or sensors with the photonic infrastructure underpinning modern communications. 

“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 David Awschalom, the Liew Family Professor of Molecular Engineering and Physics at UChicago and principal investigator.

Because erbium molecules use wavelengths compatible with silicon photonics, they could be incorporated directly into chip-based platforms that combine optical and microwave devices. The team said this compatibility with mature technologies could accelerate the development of integrated molecular photonic systems for quantum communication and hybrid quantum sensing.

The research also highlights the potential for molecular engineering to expand the palette of quantum materials. 

“Rare earth chemistry provided a fortuitous combination of properties that allowed us to bring these capabilities to a molecular system,” said Grant Smith, co-first author. He noted that synthetic chemistry allows quantum behavior to be tuned to a level difficult to achieve in solid-state substrates.

The study was conducted with collaborators at UC Berkeley, Argonne National Laboratory, and Lawrence Berkeley National Laboratory, and was supported by the U.S. Department of Energy Office of Science and Q NEXT, a DOE National Quantum Information Science Research Center.

The work builds on broader efforts to create quantum networks capable of transmitting, distributing, and entangling quantum states over commercial fiber. In related research, SDxCentral has previously reported on demonstrations of quantum signals transmitted over live telecom infrastructure, such as the University of Pennsylvania's work sending quantum information through standard fiber alongside classical traffic.

Together, these advances highlight multiple routes toward quantum networking: chip-scale molecular qubits, fiber-compatible photonics, and hybrid microwave-optical interfaces. The UChicago team said that the erbium molecular platform opens opportunities across sensing, communication, and integrated quantum devices as the field pushes toward a future quantum internet.