French research institutes CEA and C12 Quantum Electronics have announced a new quantum computer design. One that can only be described as a wafer-scale engine…for quantum. In an approach to CMOS fabrication techniques and backed by CEA’s $5 billion annual funding, the companies aim to fabricate carbon nanotube-based qubits at scale – a 200mm (7.9in) wafer at a time. As a result, transistor density is now seen as a parallel to quantum density.
There have been other quantum computing designs that aim to come close to making transistors in some way. The idea is that the more compatible qubit fabrication is with that of existing silicon-centric processes (such as those in 4N or TSMC’s Intel 7), the more efficiently they can be fabricated and scaled. .
But none of the designs shown were for a full 200mm pad scale. It’s telling that in the $599.9 billion semiconductor market, only Cerebras decided to build a wafer-scale chip. The difficulties of such a design are enormous, but C12 expects to have a working, final wafer-scale prototype by 2024.
“Quantum technology holds great promise for next-generation computing but still faces significant development challenges to fabricate qubit chips,” said Sébastien Dauvé, CEO of the CEA-Leti laboratory. “Combining well-established CMOS technologies with C12’s novel approach using carbon nanotubes could accelerate progress toward commercializing quantum computing and manufacturing these chips at scale.”
C12 is confident its technologies allow for an ease of fabrication (compared to more exotic approaches to quantum computing) that approximates that of a semiconductor device and would enable a “scalable, ultra-coherent platform for ‘quantum computing’. Pierre Desjardins, CEO and co-founder of C12, said the ultimate goal is to “transfer an academic manufacturing process to an industrial-grade semiconductor manufacturing process.”
The company claims it can manufacture thousands of qubits per hour – and ultimately achieve densities on the order of “hundreds of thousands” of qubits per wafer-sized quantum computing chip. The company’s original design goal was to focus on delivering a million-qubit quantum computer. Maybe it doesn’t need to be delivered in a single wafer after all.
C12’s qubit design begins with growing ultra-pure carbon nanotubes, which the company does within its facilities to ensure their level of purity. Then, by chemical vapor deposition, the C12 isotopes of carbon are meticulously placed – atom by atom – to form the structure of the nanotube.
It is unavoidable because the presence of any other isotope (or atomic particle) in the nanotubes would cause them to interact. This, in turn, would increase the dreaded “spin noise” – one of the main sources of disturbances within quantum machinery that can cause qubits to collapse completely, causing miscalculations or interrupting workloads. So before using nanotubes anywhere, they screened them for non-invasive impurities. Only those with 99% purity (meaning they contain 99% C12 carbon isotopes) proceed to the next step.
The carbon tubes are then meticulously placed on IC chips produced on a large scale already by the semiconductor manufacturing industry. The carbon nanotubes are suspended above an array of grid electrodes, providing optimized environmental isolation for “significantly reducing decoherence due to loading and mechanical noise.” A new regulator based on microwaves makes it possible to couple the qubits of the system with each other at will. It simultaneously improves performance while reducing environmental interference from qubit state changes.
Given the already abundant inspiration from the semiconductor industry, the idea that two such wafer-scale computer chips could then scale through a networking solution (perhaps based on photonics) looks like the later path of least resistance.
We have to remember that the announcement comes before a working prototype – but after the actual hardware test is already running. Today, IBM’s Eagle quantum computer has 127 qubits, and IBM has previously said it will reach a million-qubit density by 2030. So with CEA’s million-qubit prototype and C12 expected for 2024, there is a real contender for pole position in this particular area. race. But many metrics are responsible for the performance of a quantum computing system, and other companies (like the incomparably rich Microsoft) are definitely in the running.