University of Illinois Urbana-Champaign Develops Quantum Chip for Photon Storage

New research from The Grainger College of Engineering at the University of Illinois Urbana-Champaign has addressed a critical challenge in quantum information systems: the long-term storage of photons. Quantum information, transported by particles of light called photons, often needs to be temporarily paused while slower quantum operations catch up. This storage must occur on microchips as small as 1 centimeter (0.4 inches), a distance light covers in mere trillionths of a second, making storage for even a microsecond a significant leap.

The research, led by physics professor Elizabeth Goldschmidt and published in Nano Letters, details an integrated on-chip nanophotonic platform capable of longer-term photon storage. This platform leverages the versatility of spectral hole burning and the scalability of thin-film lithium niobate (TFLN), suggesting potential for scalable manufacturing applicable to both classical and quantum photonics. Priyash Barya, an electrical engineering graduate student and co-first author, stated that no one else has stored light on a chip in this manner with such scalability potential, calling it a "futuristic platform with industry scalability."

Conventional photonics, which uses macroscopic components like optical fibers and mirrors, can delay light by extending its travel path, but photons are easily absorbed over longer distances, making this method inefficient for quantum-relevant delays. Alternatively, coupling photons to highly coherent atoms offers longer storage but is difficult to integrate with scalable nanophotonic platforms. Daren Chen, a physics graduate student and co-first author, noted that "Long delays are an outstanding problem in quantum information processing."

Goldschmidt's lab tackled this by fabricating a nanoscale waveguide from TFLN, a material known for strong light confinement, low optical loss, and wafer-scale integration, doped with erbium atoms possessing desirable quantum properties. A tunable laser was used to spectrally arrange these atoms into an atomic frequency comb, enabling them to temporarily "catch" and "hold" incoming photons for a predetermined time. The resulting device achieved high-fidelity preservation of quantum information, with storage times exceeding 1 microsecond and the ability to store multiple photons simultaneously. Importantly, the platform is designed for commercial scalability and ease of replication. Goldschmidt emphasized that this is "not a one-off bespoke device," highlighting its simplicity and potential for commercial production by non-specialists in quantum optics.

Goldschmidt envisions this pioneering platform as a crucial step towards integrating quantum memories into scalable, chip-based quantum computers and communication networks. Future efforts will focus on improving retrieval efficiency and extending storage times by enhancing the frequency comb and experimenting with different erbium isotopes that are more impervious to noise. The lab is also exploring additional applications for this technique, building capabilities in this integrated photonics platform for other quantum photonic devices.

What to watch: Further developments in improving retrieval efficiency and storage times for this scalable quantum memory platform.

Editor's note: The draft accurately captures the technical achievements, the research context, and the quotes from the lead researchers as provided in the source.