University of Chicago Achieves Quantum Breakthrough

In a significant advancement for quantum communication, researchers at the University of Chicago have developed a method to construct rare-earth crystals atom by atom, achieving unprecedented material purity. This breakthrough has extended quantum coherence times from 0.1 milliseconds to over 10 milliseconds, with some experiments reaching 24 milliseconds. Such improvements could potentially expand quantum communication distances from a few kilometers to approximately 2,000 kilometers, bringing the concept of a global quantum internet closer to reality. The study was published in Nature Communications on November 6, 2025.

Quantum coherence refers to the duration a quantum system maintains its quantum state before decoherence leads to the loss of quantum information. Extending coherence times is crucial for developing quantum networks, as longer coherence times allow quantum information to be preserved over greater distances. Previous methods to enhance coherence times included using optical traps to confine atoms, achieving storage times on the order of microseconds. Other approaches involved using cross-correlation of noise sources to extend coherence times by a factor of ten.

The University of Chicago team, led by Assistant Professor Tian Zhong, employed a technique called molecular-beam epitaxy (MBE) to construct rare-earth doped crystals atom by atom. This method contrasts with the traditional Czochralski process, which involves melting and slowly cooling materials to form crystals. MBE allows for the precise layering of atoms, resulting in materials with exceptional purity and significantly reduced defects.

By utilizing MBE, the researchers increased the coherence time of individual erbium atoms from 0.1 milliseconds to over 10 milliseconds, with some experiments achieving 24 milliseconds. This substantial improvement suggests that quantum communication distances could be extended from a few kilometers to approximately 2,000 kilometers. For instance, a quantum computer located at the University of Chicago could potentially connect with another device as far away as Salt Lake City, Utah.

The extension of coherence times is a pivotal step toward realizing a global quantum internet. Longer coherence times enable the maintenance of quantum entanglement over extended distances, which is essential for secure quantum communication and distributed quantum computing. This development addresses one of the major obstacles in building large, reliable quantum networks.

Assistant Professor Tian Zhong highlighted the significance of this advancement, stating, "For the first time, the technology for building a global-scale quantum internet is within reach."

Prior to this breakthrough, quantum communication was limited to distances of a few kilometers due to rapid decoherence. Techniques such as using optical traps and cross-correlation of noise sources had achieved coherence times on the order of microseconds to milliseconds. The current achievement of extending coherence times to over 10 milliseconds represents a significant leap forward, potentially enabling quantum communication over continental distances.

This breakthrough by the University of Chicago marks a significant milestone in the pursuit of a global quantum internet, bringing theoretical concepts closer to practical implementation.