Silicon Quantum Computing (SQC) has achieved a milestone in the silicon modality by demonstrating a multi-register quantum processor where qubit quality increases as the system scales. Detailed in Nature, the research highlights an 11-qubit atom processor in isotopically purified silicon-28, achieving gate fidelities between 99.10% and 99.99%. This result contrasts with typical quantum architectures where increasing qubit counts often lead to declining performance due to noise and crosstalk.
The processor architecture utilizes precision-placed phosphorus atoms within silicon, patterned with 0.13-nanometer accuracy via scanning tunneling microscope (STM) lithography. The system is composed of two multi-nuclear spin registers (one with four nuclei and another with five) that are interconnected via an electron exchange interaction. This hybrid approach uses nuclear spins as high-coherence data qubits (T2Hahn up to 660 ms) and shared electrons as ancillary qubits for quantum non-demolition (QND) readout and multi-qubit control.
Technical highlights of the SQC processor include:
- Scale-Up Fidelity: Demonstrated single-qubit gate fidelities reaching 99.99% (for n5) and two-qubit electron CROT gate fidelities of 99.64%.
- Inter-Register Link: Established a quantum link between distant spin registers using a fast (1.25 μs) exchange-based CROT gate, enabling non-local entanglement across the device.
- Efficient Calibration: Implemented a recalibration protocol that scales linearly with the number of registers. By measuring a single reference peak, the system can infer the positions of all other resonance frequencies, reducing the total required calibration measurements from 96 down to two.
- GHZ State Generation: Successfully entangled up to eight nuclear spins, demonstrating the all-to-all connectivity required for fault-tolerant algorithms.
By leveraging the manufacturing precision of atom-scale placement with the scalability of existing silicon semiconductor fabrication, SQC aims to bridge the gap toward million-qubit systems. This achievement follows the company’s progression to Stage B of DARPA’s Quantum Benchmarking Initiative and its recent delivery of a rack-mounted system to the Australian Defence sector.
Read the official press release from Silicon Quantum Computing here and the full technical paper in Nature here.
February 4, 2026