Packaged circuit board containing the chip placed under microscope in probestation during an experiment. Credit: Boston University.
An interdisciplinary academic team from the USA has integrated quantum light sources and control electronics on a single chip.
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.
The system combines quantum light sources and stabilising 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.
A senior author on the study, Miloš Popović, associate professor of electrical and computer engineering at BU, said: “Quantum computing, communication, and sensing are on a decades-long path from concept to reality.
“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.”
Prem Kumar, professor of electrical and computer engineering at Northwestern and a pioneer in quantum optics added: “The kind of interdisciplinary collaboration this work required is exactly what’s needed to move quantum systems from the lab to scalable platforms.
“We couldn’t have done this without the combined efforts in electronics, photonics, and quantum measurement.”
Quantum light factories
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 millimetre by a millimetre 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.
Integrated system
To address this challenge, the team built an integrated system that actively stabilises 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.
Anirudh Ramesh, a PhD student at Northwestern who led the quantum measurements, said: “What excites me most is that we embedded the control directly on-chip – stabilising a quantum process in real time. 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.
Imbert Wang, a PhD student at Boston University who led the photonic device design, said: “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.
“That enabled co-design of the electronics and quantum optics as a unified system.”
Because the chip uses built-in feedback to stabilise each source, it behaves predictably despite temperature changes and fabrication variations – an essential requirement for scaling up quantum systems.
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.
The study is published in Nature Electronics.
