Amazon Braket now offers access to Rigetti’s Cepheus-1-108Q, a superconducting quantum processing unit featuring 108 qubits and the first gate-based quantum device with over 100 qubits available on the service. The new processor replaces the Ankaa-3 system and utilizes Rigetti’s multi-chip architecture, tiling twelve 9-qubit chiplets into a single processor. This design builds upon the Cepheus-1-36Q system, tripling both the number of chiplets and the total qubit count. Customers can utilize the device for on-demand access, priority access through Amazon Braket Hybrid Jobs, or dedicated reservations, with the system providing 20 hours of quantum task processing availability every day.
Rigetti Cepheus-1-108Q Launch on Amazon Braket
Rigetti’s newly launched Cepheus-1-108Q processor boasts 108 qubits, marking the first time a gate-based quantum device exceeding 100 qubits has become available on Amazon Braket. This increase in qubit count expands the potential complexity of quantum computations accessible to researchers and developers. The device, physically located in the United States within the US West (N.) region, is not simply a numerical upgrade, but a demonstration of Rigetti’s evolving approach to quantum processor design. It utilizes a modular multi-chip architecture, tiling twelve 9-qubit chiplets together to create a single, more powerful processor. The Cepheus-1-108Q offers customers multiple access options, including on-demand processing, priority access via Amazon Braket Hybrid Jobs for variational quantum algorithms, and dedicated reservations through Braket Direct, all designed to accommodate diverse workflows.
A key architectural shift with the Cepheus generation is the implementation of CZ (controlled-phase) gates, replacing the iSWAP gates found in previous Rigetti QPUs like Ankaa-2 and Ankaa-3. While iSWAP gates offered expressivity for near-term applications, CZ gates are more suited for the parity-check circuits crucial for error correction. According to Amazon Braket’s launch announcement, “At launch, the device achieved a median two-qubit gate fidelity of 99.1% with gate speeds of approximately 60 nanoseconds.” Rigetti and Amazon Braket also emphasize the importance of qubit selection for optimal performance. Superconducting quantum devices inherently exhibit variations in qubit fidelity, and on a 108-qubit system, identifying the highest-performing subset is critical. Amazon Braket provides up-to-date calibration data, including single- and two-qubit gate fidelities and readout errors, enabling customers to analyze performance and select qubits tailored to their specific workloads. Researchers can even utilize tools to identify a high-fidelity 50-qubit chain, as demonstrated by an example using a subgraph isomorphism routine applied to the device’s calibration data; this allows for focused computation on the most reliable qubits, potentially improving overall results.
Cepheus-1-108Q Modular Multi-Chip Architecture
The pursuit of practical quantum computation increasingly focuses on scaling qubit counts while maintaining fidelity, a challenge currently addressed through diverse architectural approaches. This new system doesn’t simply add qubits to a pre-existing design, but implements a fundamentally different construction method centered around modularity. This approach represents a departure from monolithic designs, where all qubits reside on a single die, and allows for a more manageable fabrication process and potentially improved yield. Each of these chiplets is based on superconducting transmon qubits arranged in a square lattice, with each qubit connecting to up to four nearest neighbors. Rigetti incorporated an adiabatic CZ gate scheme, designed to reduce incoherent and leakage errors, enabling customers to run deeper circuits with lower accumulated error.
1% Two-Qubit Gate Fidelity & Performance Metrics
Rigetti Computing is focused on refining the performance characteristics of its latest quantum processor, the Cepheus-1-108Q, with a particular emphasis on gate fidelity and its implications for complex quantum computations. While the figure of 108 qubits captures attention, the underlying improvements in qubit control and coherence are crucial for realizing practical quantum advantage. The Cepheus-1-108Q represents a shift in native gate design, moving from iSWAP gates, utilized in previous Rigetti QPUs such as Ankaa-2 and Ankaa-3, to CZ (controlled-phase) gates. This change isn’t merely aesthetic; CZ gates are considered more suitable for parity-check circuits essential for error correction schemes. This architectural refinement is coupled with an adiabatic CZ gate implementation, designed to minimize both incoherent and leakage errors.
This allows researchers to construct and execute deeper circuits, pushing the boundaries of what’s possible with near-term quantum hardware. The device achieved 99.1% fidelity with gate speeds of approximately 60 nanoseconds, a significant step towards reducing the accumulation of errors during calculations. Rigetti doesn’t simply report these figures; they are made readily available to users. “For up-to-date characterization data, including gate fidelities, coherence times, and connectivity information, visit the Cepheus-1-108Q device page in the Amazon Braket Management Console or query the device properties using the Braket Python SDK,” the company states, highlighting a commitment to transparency and user control. Beyond overall fidelity, Rigetti and Amazon Braket are addressing the inherent variability in qubit performance within the 108-qubit system. Superconducting quantum devices inevitably exhibit differing characteristics due to manufacturing tolerances and environmental influences. This allows customers to strategically select the highest-performing qubits for their specific algorithms.
Researchers can then employ subgraph isomorphism routines to identify optimal qubit chains, as demonstrated by a selected 50-qubit chain with demonstrably lower error rates than the device median. This granular level of control and data access is intended to empower users to maximize the potential of the Cepheus-1-108Q and accelerate progress in quantum computing applications.
While iSWAP gates have strong expressivity for NISQ-era applications, CZ gates are the more natural native gate for parity-check circuits used in error correction.
Braket Pulse & High-Fidelity Qubit Selection
The demand for reliable quantum computation increasingly focuses on maximizing performance from available hardware, and Amazon Braket’s new Rigetti Cepheus-1-108Q processor offers tools to address this challenge directly. Beyond simply increasing qubit count to 108, the first gate-based quantum device exceeding 100 qubits on the platform, Rigetti and Amazon have integrated features allowing users to refine qubit selection and optimize circuit execution at a fundamental level. This granular control is particularly crucial given that even within a single quantum processor, qubit fidelity isn’t uniform; variations arise from manufacturing imperfections and environmental noise. A key capability is the availability of Braket Pulse, which allows researchers to bypass pre-defined gate instructions and directly manipulate the analog control signals sent to individual qubits. This pulse-level access is not merely for advanced users; it facilitates detailed study of noise characteristics, development of customized gates, and implementation of sophisticated error mitigation strategies.
Understanding these nuances is essential for extracting meaningful results from near-term quantum devices. Rigetti’s architecture, tiling twelve 9-qubit chiplets, further complicates the optimization process, requiring careful consideration of qubit connectivity and potential crosstalk between chiplets. To aid in this process, Amazon Braket provides comprehensive, up-to-date calibration data for every qubit and qubit pair on the Cepheus-1-108Q. “By plotting the error distributions for the selected region, we can compare against the median device statistics,” explains the team. This targeted approach, combined with tools for allocating qubits on the processor, promises to significantly improve the reliability and accuracy of quantum computations performed on the Cepheus-1-108Q, and potentially other future devices.
