New research reveals that metasurfaces can act as powerful building blocks for quantum optical networks
This breakthrough could replace bulky components like waveguides, mirrors, and beam splitters with a single flat device
Researchers used graph theory to design and control the complex quantum behaviors directly on the metasurface
Photon Power: The Quest for Scalable Quantum Devices
As researchers work to make quantum computers and networks more practical, photons—the basic particles that make up light—are emerging as promising candidates for moving information quickly, even at room temperature. Typically, guiding photons into the right quantum states involves complex arrangements of waveguides on large microchips, or clunky setups built with lenses, mirrors, and beam splitters. These components allow photons to become entangled, a key quantum process that lets them carry and process information in parallel. However, building and maintaining such intricate systems is challenging because they rely on large numbers of delicate parts, making it hard to scale.
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Harvard Just Collapsed a Quantum Computer Onto a Chip
By Anne J. Manning, Harvard John A. Paulson School of Engineering and Applied SciencesJuly 30, 2025No Comments5 Mins Read
Metasurface Quantum Graphs
Artistic representation of metasurface quantum graphs. Credit: Joshua Mornhinweg
Harvard engineers have built a chip-thin metasurface that replaces entire quantum optical setups.
New research reveals that metasurfaces can act as powerful building blocks for quantum optical networks
This breakthrough could replace bulky components like waveguides, mirrors, and beam splitters with a single flat device
Researchers used graph theory to design and control the complex quantum behaviors directly on the metasurface
Photon Power: The Quest for Scalable Quantum Devices
As researchers work to make quantum computers and networks more practical, photons—the basic particles that make up light—are emerging as promising candidates for moving information quickly, even at room temperature. Typically, guiding photons into the right quantum states involves complex arrangements of waveguides on large microchips, or clunky setups built with lenses, mirrors, and beam splitters. These components allow photons to become entangled, a key quantum process that lets them carry and process information in parallel. However, building and maintaining such intricate systems is challenging because they rely on large numbers of delicate parts, making it hard to scale.
What if all those components could be replaced by a single, ultra-thin surface that manipulates light in exactly the same way—while using far fewer fabricated elements?
Harvard’s Breakthrough in Flat Quantum Optics
A research team at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) achieved just that. Led by Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, the group developed specialized metasurfaces. These flat devices are engraved with nanoscale patterns that control light and serve as compact replacements for traditional quantum-optical hardware.
The study was published in Science and received funding support from the Air Force Office of Scientific Research (AFOSR).
Scaling Quantum Systems with Simplicity
The team demonstrated that a metasurface can generate entangled photon states and perform complex quantum operations—just like larger optical systems that use many separate components.
“We’re introducing a major technological advantage when it comes to solving the scalability problem,” said graduate student and first author Kerolos M.A. Yousef. “Now we can miniaturize an entire optical setup into a single metasurface that is very stable and robust.”
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