UChicago Pushes Quantum Internet Within Reach With 24 ms Coherence

A new way of growing rare-earth crystals boosts quantum coherence from 0.1 ms to over 10 ms, enabling quantum links over thousands of kilometers.

Quantum networks have long been limited by one brutal constraint: how long a qubit can stay coherent while you try to entangle it with another across an optical fiber. A team at the University of Chicago’s Pritzker School of Molecular Engineering has now shown that this “clock” can be stretched dramatically, bringing a true quantum internet closer than ever. 

What the researchers achieved

In a study published in Nature Communications on November 6, 2025, Tian Zhong’s group demonstrated a new spin–photon interface based on erbium atoms embedded in a specially grown crystal. The key result:

• They increased the coherence time of individual erbium ions from around 0.1 milliseconds to more than 10 milliseconds,

• And in the best case reached about 24 milliseconds of coherence. 

At telecom wavelengths, that level of coherence is enough to support entanglement distribution over 2,000 km of fiber in realistic scenarios, and in idealized setups could stretch toward 4,000 km – distances comparable to connecting cities across continents.

The trick: molecular-beam epitaxy instead of a “melting pot”

Traditionally, rare-earth-doped crystals for quantum networking are grown using the Czochralski method – basically a controlled melt where all ingredients are mixed at ~2,000 °C and slowly cooled into a bulk crystal that is later carved into devices.

Zhong’s team took a completely different route using molecular-beam epitaxy (MBE):

• Instead of carving a sculpture out of a big block, they “3D print” the crystal atom by atom, layer by layer,

• This yields ultra-clean, low-defect crystals in their final device geometry,

• The result is a dramatic reduction in noise and decoherence for the embedded erbium ions. 

External experts in quantum networking have highlighted that this “bottom-up” approach provides a scalable path to many networkable qubits with excellent optical and spin coherence, all at telecom wavelengths and in a fiber-compatible architecture.