This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For highly fragile quantum information systems, the ability to store quantum information is vital—but also challenging. Quantum information is transported in particles of light called photons, which often must be temporarily paused (or "stored") while other, slower quantum operations catch up.
This storage must be performed on microchips as small as 1 centimeter (0.4 inches)—a distance covered by light in a few trillionths of a second. Storing photons for a microsecond would represent a massive leap forward for the capabilities of quantum chips. New research from The Grainger College of Engineering at the University of Illinois Urbana-Champaign addresses this challenge by developing an integrated on-chip nanophotonic platform for longer-term storage of photons.
The research, led by physics professor Elizabeth Goldschmidt and published in Nano Letters, describes an integrated platform that leverages the versatility of spectral hole burning and the scalability of thin-film lithium niobate, giving it potential for scalable manufacturing, with implications for both classical and quantum photonics. "No one else has stored light on a chip in a platform like this, with this potential for scalability," said Priyash Barya, an electrical engineering graduate student and the paper's co-first author. "Our technique is the only way of doing this, and we're doing it on one of the leading platforms for quantum optics and quantum information systems.
It's a futuristic platform with industry scalability." There are two broad ways to store photons. Using conventional photonics, a field that uses macroscopic components like optical fibers and mirrors, scientists can delay light by extending its travel path—but this comes at a cost. Photons are easily absorbed by matter, and traveling for longer distances increases the likelihood of absorption.
A photon is unlikely to survive the distances required for quantum-relevant delays, making conventional photonic storage highly inefficient. Alternatively, photons can be coupled to highly coherent atoms for longer storage. However, integrating such atoms with scalable nanophotonic platforms is largely out of reach.
"Long delays are an outstanding problem in quantum information processing," said Daren Chen, a physics graduate student and the paper's co-first author. "We wanted to demonstrate a very promising approach for this using our nanophotonic platform." Members of Goldschmidt's lab tackled the problem by building on previous work in rare-earth-doped materials systems and spectral hole burning–induced slow light. The Illinois researchers fabricated a nanoscale waveguide made of thin-film lithium niobate (TFLN), a material known for its strong light confinement, low optical loss and wafer-scale integration, and doped with erbium atoms, which have desirable quantum properties.
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