Three months after the delay announced in January this year, Rigetti has launched its 108-qubit quantum computing system, Cepheus™-1-108Q. The system is now accessible via the Rigetti Quantum Cloud Services (QCS®) Platform and through AWS’ Amazon Braket.
Cepheus-1-108Q is Rigetti’s highest qubit-count system to date and, like all of Rigetti’s quantum computers, utilizes a modular design based on Rigetti’s proprietary chiplet-based architecture. The system comprises twelve interconnected 9-qubit chiplets, tripling the number of qubits and chiplets from Rigetti’s previous 36-qubit system, Cepheus-1-36Q.
According to Rigetti, the system is currently performing at a 99.1% median two-qubit gate fidelity with a gate speed of ~60 ns and a 99.9% median single-gate fidelity.
“The addition of Cepheus-1-108Q to Amazon Braket gives our global customers another choice as they research quantum computing applications in materials science, optimization, and quantum simulation. As the first gate-based device on Braket with over 100 qubits, Cepheus-1-108Q delivers improved fidelities that allow customers to push to wider and deeper circuits,” said Eric Kessler, General Manager, Amazon Braket. “Rigetti was a launch partner for Amazon Braket, and we’re excited to deepen that relationship with this launch. With Cepheus-1-108Q, we bring the third generation of Rigetti devices to our customers, following Aspen and Ankaa. We remain committed to providing researchers and enterprises around the world with access to the latest quantum hardware.”
Key Technical Advancements
According to Rigetti, the new system features several significant engineering improvements designed to maintain fidelity and performance as qubit counts grow:
- Enhanced qubit and coupler design: Optimized chip design enables fast two-qubit gates and higher fidelity.
- CZ gates for error correction: Supports high-fidelity native gates and efficient circuit compilation necessary for quantum error correction and future fault-tolerant architectures. Rigetti announced it has achieved a two-qubit gate fidelity as high as 99.9% at 28 nanoseconds on a prototype system using a proprietary implementation of an adiabatic CZ gate scheme. These gates are already in use on Cepheus-1-108Q and will continue to improve as Rigetti incorporates those prototype learnings into larger systems.
- Upgraded control electronics: A newly engineered control system delivers superior signal-to-noise ratio for qubit readout.
- Advanced fabrication process: Rigetti’s Alternating-Bias Assisted Annealing technique improves qubit frequency targeting and reduces defects, contributing to higher fidelities.
During system development, Rigetti refined its architecture to mitigate coupling interactions between tunable couplers that become more pronounced beyond 100 qubits. These design improvements shifted the primary performance limitation from coupler behavior to coherence time.
Roadmap
Rigetti plans to continue to improve the fidelity of its individual chiplets and expects Cepheus‑1‑108Q to reach a median 99.5% two‑qubit gate fidelity later this year. Rigetti intends to update its technology roadmap later this year, once it has incorporated the results of this work, including how it plans to reach quantum advantage in about three years.
