First electronic–photonic quantum chip created in commercial foundry

(Press-News.org) In a milestone for scalable quantum technologies, scientists from Boston University, UC Berkeley, and Northwestern University have reported the world’s first electronic–photonic–quantum system on a chip, according to a study published in Nature Electronics . The system combines quantum light sources and stabilizing electronics using a standard 45-nanometer semiconductor manufacturing process to produce reliable streams of correlated photon pairs (particles of light)—a key resource for emerging quantum technologies. The advance paves the way for mass-producible “quantum light factory” chips and large-scale quantum systems built from many such chips working together.

“Quantum computing, communication, and sensing are on a decades-long path from concept to reality,” says Miloš Popović, associate professor of electrical and computer engineering at BU and a senior author on the study. “This is a small step on that path—but an important one, because it shows we can build repeatable, controllable quantum systems in commercial semiconductor foundries.”

“The kind of interdisciplinary collaboration this work required is exactly what’s needed to move quantum systems from the lab to scalable platforms,” says Prem Kumar, professor of electrical and computer engineering at Northwestern and a pioneer in quantum optics. “We couldn’t have done this without the combined efforts in electronics, photonics, and quantum measurement.”

Just as electronic chips are powered by electric currents, and optical communication links by laser light, future quantum technologies will require a steady stream of quantum light resource units to perform their functions.  To provide this, the researchers’ work created an array of “quantum light factories” on a silicon chip, each less than a millimeter by a millimeter in dimension.

Generating quantum states of light on chip requires precisely engineered photonic devices—specifically, microring resonators (the same devices recently identified by Nvidia CEO Jensen Huang as being integral to Nvidia’s future scaling of its AI compute hardware via optical interconnection). To generate streams of quantum light, in the form of correlated pairs of photons, the resonators must be tuned in sync with incoming laser light that powers each quantum light factory on the chip (and is used as fuel for the generation process). But those devices are extremely sensitive to temperature and fabrication variations which can push them out of sync and disrupt the steady generation of quantum light.

To address this challenge, the team built an integrated system that actively stabilizes quantum light sources on chip—specifically, the silicon microring resonators that generate the streams of correlated photons. Each chip contains twelve such sources operable in parallel, and each resonator must stay in sync with its incoming laser light even in the presence of temperature drift and interference from nearby devices—including the other eleven photon-pair sources on the chip.

“What excites me most is that we embedded the control directly on-chip—stabilizing a quantum process in real time,” says Anirudh Ramesh, a PhD student at Northwestern who led the quantum measurements. “That’s a critical step toward scalable quantum systems.”

The extreme sensitivity of the microring resonators, the building blocks for the quantum light sources, is well known and is both a blessing and a curse.  It is the reason why they can generate quantum light streams efficiently and in a minimal chip area.  However, small shifts in temperature can derail the photon-pair generation process. The BU-led team solved this by integrating photodiodes inside the resonators in a way that monitors alignment with the incoming laser while preserving the quantum light generation.  On-chip heaters and control logic continually adjust the resonance in response to drift.

“A key challenge relative to our previous work was to push photonics design to meet the demanding requirements of quantum optics while remaining within the strict constraints of a commercial CMOS platform,” says Imbert Wang, a PhD student at Boston University who led the photonic device design. “That enabled co-design of the electronics and quantum optics as a unified system.”

Because the chip uses built-in feedback to stabilize each source, it behaves predictably despite temperature changes and fabrication variations—an essential requirement for scaling up quantum systems. It was fabricated in a commercial 45-nanometer complementary metal-oxide semiconductor (CMOS) chip platform originally developed through a close collaboration between BU, UC Berkeley, GlobalFoundries, and Silicon Valley startup Ayar Labs, which grew out of research at the two universities and is now an industry leader in optical interconnect chiplets. Through the new collaboration with Northwestern, that same manufacturing process now enables not only advanced optical interconnects for AI and supercomputing, but also, as shown in the study, complex quantum photonic systems on a scalable silicon platform.

“Our goal was to show that complex quantum photonic systems can be built and stabilized entirely within a CMOS chip,” says Daniel Kramnik, a PhD student at UC Berkeley who led chip design, packaging, and integration. “That required tight coordination across domains that don’t usually talk to each other.”

As quantum photonic systems progress in scale and complexity, chips like this could become building blocks for technologies ranging from secure communication networks to advanced sensing and, eventually, quantum computing infrastructure.

Several of the graduate student authors have since continued advancing silicon photonics and quantum technologies in industry. Josep Maria Fargas Cabanillas and Anirudh Ramesh are now at photonic quantum computer startup PsiQuantum, while Ðorđe Gluhović and Sidney Buchbinder have joined Ayar Labs.  Imbert Wang is at Aurora.  Daniel Kramnik is at Google X and pursuing a silicon photonics startup. These trajectories reflect the growing momentum behind silicon photonics, both in scaling today’s AI computing infrastructure, and in the longer term for enabling scalable, chip-based quantum systems.

The research was supported by the National Science Foundation, including through its Future of Semiconductors (FuSe) program, as well as the Packard Fellowship for Science and Engineering and the Catalyst Foundation. Chip fabrication support was provided by Ayar Labs and GlobalFoundries.

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