Is this the most scalable quantum processor yet? Silicon Quantum Computing may have cracked it

Silicon Quantum Computing (SQC) has unveiled a quantum processor that reverses a long-standing limitation in quantum architecture: it improves fidelity as more qubits are added. Published in Nature, the company’s 11-qubit atom processor demonstrates record-setting performance within the silicon modality, positioning SQC at the frontier of scalable fault-tolerant quantum computing.

The breakthrough centers on an integrated dual-register design that uses phosphorus atoms in silicon, achieving two-qubit gate fidelities of up to 99.9% and Bell-state fidelities as high as 99.5%. The result not only surpasses all previous silicon-based processors in both size and quality but also suggests a credible path to modular, commercial-scale systems.

Why is fidelity improving with scale in SQC’s silicon qubit platform—and why does that change the game?

In most quantum systems, adding qubits increases error rates and destabilizes entanglement. Silicon Quantum Computing’s result inverts that trend. The new architecture demonstrates that qubit quality can improve with qubit count—an essential requirement for achieving the holy grail of fault-tolerant quantum computing.

This is not merely a theoretical exercise. The chip architecture relies on multi-nuclear spin registers, where several phosphorus atoms are placed within a few nanometers and coupled through hyperfine interactions with a shared electron. These local spin registers are then linked through electron exchange interaction, extending entanglement across the device. What stands out is that entanglement fidelity not only held up across this design—but in some cases improved—especially in Bell-state fidelities between nuclear-spin pairs.

SQC’s ability to deliver gate fidelities between 99.10% and 99.99% even as more registers are introduced suggests a level of architectural robustness that the quantum industry has struggled to achieve, particularly in noisy intermediate-scale quantum (NISQ) devices. Many platforms—trapped ions, superconducting qubits, photonic systems—encounter fundamental limitations as they scale. SQC’s approach appears to mitigate some of those constraints through careful materials engineering, quantum control, and architectural modularity.

What makes the silicon modality so critical in the long-term race for quantum computing infrastructure?

Silicon as a modality enjoys a near-unmatched advantage: it rides on the back of trillions of dollars of legacy semiconductor investment. Fabrication tools, wafer processing pipelines, and atomic-scale control infrastructure already exist—albeit for classical chips.

By leveraging silicon, SQC avoids reinventing the materials stack from scratch. The company’s chip fabrication process is itself a standout, delivering atomically precise placement of phosphorus dopants within ultrapure silicon wafers at sub-nanometer resolution. SQC claims 0.13 nanometer precision—arguably the most accurate in the semiconductor industry.

This atomic control is not academic. It directly enables the design of controllable hyperfine couplings between nuclear and electron spins, which is what allows coherent multi-qubit control across registers. Long coherence times—extending to seconds for nuclear spins—combined with this control have enabled SQC to implement high-fidelity versions of complex quantum gates and algorithms like Grover’s search algorithm.

In effect, SQC is turning silicon into a quantum-grade material, closing the historical gap between CMOS-classical and quantum-class computing.

How does the 11-qubit processor benchmark against peer platforms—and what’s next?

SQC’s 11-qubit device now stands as the most advanced silicon-based quantum processor by number of qubits, fidelity, and entanglement reach. Compared to Intel’s tunnel-coupled quantum dot arrays, SQC’s atom-based registers show higher fidelity. Against superconducting qubit systems like those from International Business Machines Corporation or Google, SQC’s processor offers a smaller qubit count but potentially longer coherence and stronger scaling symmetry.

The processor uses two spin registers—a 4P and a 5P nuclear register—linked by electron exchange interaction. The ancilla spins (electron spins co-located with the phosphorus nuclei) enable rapid control and entanglement between nuclear spins across both registers. Using tailored calibration routines that scale linearly with register count, SQC entangled every local and non-local pair in the system, achieving Bell-state fidelities from 91.4% to 99.5% within registers, and from 87.0% to 97.0% across registers.

In a further demonstration of systemwide coherence, the team generated GHZ states involving up to eight nuclear spins—an advanced benchmark in multiqubit entanglement, especially within a solid-state architecture.

These achievements move SQC into the elite tier of quantum hardware companies with realistic ambitions for error-corrected computing.

What are the commercial and institutional implications of this breakthrough?

SQC is already translating its scientific leadership into commercial traction. Telstra Corporation has reported significant reductions in training time for machine learning models using SQC’s quantum ML platform. The Australian Department of Defence has procured a rack-mounted version of SQC’s system for internal research. Additionally, the company has advanced to Stage B of DARPA’s Quantum Benchmarking Initiative, signaling growing U.S. institutional interest in its architecture.

This dual-front strategy—scientific leadership backed by institutional adoption—is rare in quantum. Many startups, including those in North America and Europe, have yet to demonstrate this level of real-world deployment despite larger valuations and funding pools.

SQC’s alignment with defense, telecom, and sovereign computing agendas in Australia and beyond may position it as a trusted supplier of quantum infrastructure in national security contexts.

What execution risks still remain for silicon quantum scalability—and how is SQC addressing them?

Despite the record-setting performance, challenges remain. Current gate operations assume that “spectator qubits”—those not actively used in a gate—remain pre-initialized. SQC plans to move beyond this with future benchmarks involving arbitrary spectator states, using more advanced techniques like modified randomized benchmarking, gate-set tomography, and non-Markovian process analysis.

Moreover, limitations around hyperfine coupling strength—which governs gate speed—still exist. SQC plans to address this through atomic-level engineering of the phosphorus placement to optimize these couplings.

A particularly important frontier will be implementing a universal geometric CZ gate, requiring parallelized drive execution and precision pulse shaping. These are non-trivial, but SQC’s control roadmap suggests it has already started developing calibration strategies to offset challenges like microwave-induced frequency shifts.

Put simply: while SQC’s progress is substantial, scaling to 100 or 1,000-qubit fault-tolerant devices will still require multiple layers of engineering innovation.

How does this reshape the competitive map for quantum computing leadership?

The latest announcement is not merely an academic paper—it reshuffles the race.

While superconducting qubit companies like International Business Machines Corporation and Google continue to scale via error correction code pathways (such as surface codes), SQC is betting on a fundamentally different material stack that scales with lower overhead and potentially longer coherence. Trapped ion companies like IonQ, Inc. tout fidelity but struggle with scaling and integration density. Photonics companies often face losses and manufacturing complexity.

SQC’s play is silicon-native, integration-friendly, and modular. And it’s one of the few companies that fully manufactures its own QPUs—meaning fewer external dependencies.

If the fidelity scaling curve holds across larger systems, SQC may unlock not just a high-performance modality—but the most manufacturable one.

What are the key takeaways from SQC’s record-setting silicon quantum processor announcement?

• Silicon Quantum Computing demonstrated an 11-qubit atom processor with record-setting fidelities, showing improved qubit quality with increased system size.
• The processor’s architecture links two multi-nuclear spin registers using electron exchange, achieving Bell-state fidelities up to 99.5%.
• The company has achieved fidelities of 99.10% to 99.99% for single- and multi-qubit gates, supporting execution of GHZ states across eight nuclear spins.
• This fidelity scaling trend reverses a major bottleneck in quantum architecture, supporting a path toward fault-tolerant, modular systems.
• SQC is uniquely positioned as the only private firm that manufactures its own quantum chips using atomic-level phosphorus placement in silicon.
• Commercial traction includes deployments with Telstra Corporation and the Australian Department of Defence, and advancement in DARPA’s benchmarking program.
• Execution risks remain around spectator qubit interference, gate speed tuning, and complex multi-qubit calibration, which the company is actively addressing.
• If sustained, SQC’s silicon modality could emerge as the most manufacturable and scalable platform in the quantum race.