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27 Feb 2025
Nature paper details manufacturable platform with silicon nitride waveguides and barium titanate switches.
PsiQuantum, the Silicon Valley photonic quantum computing startup, is claiming a significant breakthrough with a new high-volume process it says will be capable of manufacturing million-qubit-scale systems.
The Palo Alto firm, which raised $450 million in a BlackRock-led investment in 2021, has revealed details of “Omega”, a quantum photonic chipset purpose-built for utility-scale quantum computing, in a scientific paper just published in the journal Nature
It details a chipset designed and fabricated on full-size silicon wafers at the GlobalFoundries silicon photonics fab in New York, with key components including high-performance, single-photon sources, superconducting single-photon detectors, and a “next-generation” optical switch based on barium titanate.
“Every photonic component is demonstrated with beyond-state-of-the-art performance,” claims the firm. “The paper shows high-fidelity qubit operations, and a simple, long-range chip-to-chip qubit interconnect – a key enabler to scale that has remained challenging for other technologies.
“The chips are made in a high-volume semiconductor fab, representing a new level of technical maturity and scale in a field that is often thought of as being confined to research labs.”
Citing high-performance operating figures including a chip-to-chip quantum interconnect fidelity of 99.72 per cent, PsiQuantum added that it will break ground this year on two data center-scale quantum computing centers, one in Brisbane, Australia, and another in Chicago.
Pushing boundaries
PsiQuantum co-founder and CEO Jeremy O’Brien said of the latest advance: “For more than 25 years it has been my conviction that in order for us to realize a useful quantum computer in my lifetime, we must find a way to fully leverage the unmatched capabilities of the semiconductor industry. This paper vindicates that belief.”
GlobalFoundries CEO Thomas Caulfield added: “Semiconductor manufacturing will inevitably be a large part of any solution to building quantum computers at scale.
“Our partnership combines GlobalFoundries’ world-class photonics manufacturing with PsiQuantum’s advanced capability in photonic quantum computing, and the results so far have been remarkable.
“We look forward to pushing these boundaries even further as we work toward large-scale quantum systems.”
The chip maker said in January that it was planning to spend upwards of $700 million establishing a new silicon photonics facility at its existing upstate New York location near the Albany semiconductor technology development hub.
Highlighting the manufacturability and connectivity of PsiQuantum’s approach, the startup’s chief technologist and co-founder Mark Thompson noted: “Our technology is manufactured in a high-volume semiconductor fab that normally produces chips for cell phones and the automotive industry and now yields the world's highest-performance photonic qubits.
“We can also seamlessly connect our chips together using conventional optical fibers, allowing us to rapidly scale-up our systems and deliver truly powerful quantum computers.”
Beyond the lab
The latest work is said to build on initial research carried out two decades ago at the University of Queensland in Brisbane, where O’Brien was a senior research fellow. At that time O’Brien and colleagues realized the first two-qubit gate for single photons.
By adopting silicon photonics technology now deployed widely in data centers, PsiQuantum says it has now built the full technology stack required to generate, manipulate, transmit and detect photonic qubits within integrated quantum circuits.
“The critical components include waveguides, beamsplitters, bends, couplers, single-photon sources, single-photon detectors, fast optical switching and chip-to-fiber input/output coupling,” says the firm.
”All of these components existed in some form before we started the company, but we knew that for use in a quantum computer we would need to integrate these components together into a high-volume manufacturing process and improve their performance dramatically.”
Pete Shadbolt, another PsiQuantum co-founder and now its chief scientific officer, says that the latest development moves the firm’s technology beyond a science project.
“Before we started PsiQuantum, my co-founders and I were in a university lab playing around with a couple of qubits but we knew then that the platform we were using was sorely deficient,” he commented.
“We knew that we needed millions of qubits and we knew that implied getting into a mature fab, integration of unlikely components together into a single platform, and climbing a performance curve that at the time seemed borderline impossible.
“It has been amazing to see how the team has executed on those plans from a decade ago, and it is tremendously exciting to now have the technology in our hands that we will use to build the first commercially useful systems.”
Niobium nitride and barium titanate
Two of the more recent developments are a superconducting thin film of niobium nitride to enable highly efficient single-photon detection, and the use of barium titanate - an ultra-high-performance electro-optic material - to enable fast photon routing.
“PsiQuantum has made and tested millions of devices and thousands of wafers of silicon, and today we perform around half a million device-level measurements per month,” points out the firm.
Another key consideration is system cooling, and PsiQuantum says that photonic quantum computing allows a fundamentally different approach to the “chandelier” style cryogenics usually adopted.
“We have eliminated the chandelier in favor of a simpler, more powerful, and more manufacturable cuboid design, closer to the form factor of a standard data center server rack,” stated the firm, adding that it operated at a temperature of 2-4 K, rather than the milli-Kelvin level more typical of quantum computing.
“Instead of fragile, bespoke refrigeration systems, our design integrates seamlessly with large-scale cryoplants, similar to those used in particle accelerators and fusion reactors.”
Pointing out that the next step would be to optically interconnect the quantum chipsets, the company suggests that the Omega platform fundamentally changes the outlook for photonics quantum computing.
“We now have the technology to manufacture and cool as many quantum chips as we could ever need. While we will continue refining performance and scaling production, the primary challenge ahead is systems integration: wiring these chips together into increasingly powerful systems.”
Specific refinements already identified include a further reduction in silicon nitride material and component losses, improved filter performance, and higher detector efficiency to push overall photon loss and fidelity.
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