Rigetti Cepheus: Superconducting Quantum Computing at Scale on Open Quantum
Access Rigetti's 108-qubit Cepheus-1 superconducting processor with 99.1% CZ gate fidelity and 99.9% single-qubit fidelity through a unified cloud API.
Rigetti's Cepheus-1-108Q is a 108-qubit superconducting quantum processor built on transmon qubits arranged in a square lattice topology with tunable couplers. It achieves 99.1% two-qubit CZ gate fidelity and 99.9% single-qubit gate fidelity, optimized for fast gate times while reducing coherent errors. The tunable coupler architecture allows dynamic control over qubit-qubit coupling strength, enabling parametric compilation techniques that optimize circuit execution. The square lattice provides 4-fold nearest-neighbor connectivity, offering more routing options than linear or heavy-hex topologies and reducing SWAP overhead for circuits requiring non-adjacent qubit interactions. Fabricated at Rigetti's Fab-1 facility using superconducting through-silicon vias and flip-chip cap bonding, Cepheus-1 is designed for production quantum workloads and hybrid quantum-classical algorithms. Rigetti Cepheus-1 is available on Open Quantum through the same unified API used to access QPUs from IonQ, IQM, and AQT, with $50 of free quantum compute credits every 90 days to start running circuits and comparing results across providers immediately.
About Rigetti Computing
Founded in 2013 by Chad Rigetti, a former IBM researcher, Rigetti Computing is a full-stack quantum computing company headquartered in Berkeley, California. The company designs, fabricates, and operates its own superconducting quantum processors in its dedicated Fab-1 fabrication facility, making it one of the few quantum companies with end-to-end vertical integration.
Rigetti developed the Quil (Quantum Instruction Language) programming language and the Forest SDK, an open-source developer suite that includes the pyQuil Python library, the Rigetti Quil Compiler, and the Quantum Virtual Machine. The Forest SDK provides fine-grained pulse-level control for researchers who need direct hardware access.
Publicly traded on NASDAQ under the ticker RGTI, Rigetti entered a $200M strategic partnership with Quanta Computer in 2025 to scale quantum processor production and establish co-located quantum-classical data centers.
Full-Stack Vertical Integration
Rigetti designs and fabricates its own QPUs in-house at Fab-1, maintaining control over the entire hardware stack from chip design to cloud delivery.
Modular Chiplet Architecture
The Cepheus-1-36Q (August 2025) demonstrated the modular chiplet architecture with interconnected 9-qubit chiplets. Cepheus-1-108Q is the production realization, scaling to 108 qubits using superconducting through-silicon vias and flip-chip cap bonding.
Multi-Cloud Availability
Rigetti hardware is available via Rigetti QCS, Amazon Braket, Microsoft Azure Quantum, and now Open Quantum.
Rigetti Hardware on Open Quantum
| System | Qubits | 2Q Gate Fidelity | Connectivity | Best For |
|---|---|---|---|---|
| Cepheus-1-108Q | 108 | 99.1% CZ | Square lattice (4-fold nearest-neighbor) | Production workloads, hybrid algorithms |
| Ankaa-3 Sunset Q2 '26 | 84 | 99.0% CZ | Square lattice (4-fold nearest-neighbor) | Replaced by Cepheus-1 |
Fast Gates, Reduced Coherent Errors
Rigetti's Cepheus-1 uses native CZ (Controlled-Z) entangling gates optimized for fast execution while reducing coherent errors. Fast gates mean more operations can be completed within the coherence window of the qubits (T1: 25 microseconds, T2: 10 microseconds), enabling deeper circuits and more complex algorithms. The tunable coupler architecture allows dynamic control over qubit-qubit coupling strength, enabling parametric compilation techniques that further optimize circuit execution.
Key Performance Highlights
- 99.1% two-qubit CZ gate fidelity, 99.9% single-qubit gate fidelity
- T1: 25 microseconds, T2: 10 microseconds
- Square lattice with 4-fold connectivity for efficient circuit mapping
- Tunable coupler architecture for efficient qubit-qubit coupling
Why Run Rigetti Circuits on Open Quantum?
Unified API
Access Rigetti, IonQ, AQT, and IQM hardware through a single SDK. No need to learn Quil or set up the Forest SDK.
No Vendor Lock-In
Write your circuit once in Qiskit or PennyLane and run it on any backend. Switch between vendors freely.
Cross-Vendor Benchmarking
Compare Rigetti superconducting results with IonQ and AQT trapped-ion results on the same circuit.
Free $50 of Compute
Every new Open Quantum account includes $50 of free quantum compute, refreshed every 90 days. Start running circuits on Rigetti immediately.
Getting Started
Submit your first circuit to Rigetti's Cepheus-1 in minutes. Install the Open Quantum SDK, authenticate, and select the Rigetti backend.
from openquantum_sdk.clients import SchedulerClient, JobSubmissionConfig
scheduler = SchedulerClient() # uses OPENQUANTUM_CLIENT_ID/SECRET env vars
config = JobSubmissionConfig(
backend_class_id="rigetti:cepheus-1-108q",
name="Bell State on Rigetti",
shots=100,
)
job = scheduler.submit_job(config, file_path="bell_state.qasm")
result = scheduler.download_job_output(job)$50 of Free Quantum Compute
Every new Open Quantum account includes $50 of free quantum compute credits, refreshed every 90 days. Run circuits on Rigetti, IonQ, AQT, and IQM hardware at no cost.
Frequently Asked Questions
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