3D-integrated 25-qubit quantum annealing processor with high coherence, individualized control, and modular architecture. Part 2: characterization.*

We have designed, fabricated, and measured an advanced quantum annealing processor comprised of 25 capacitively-shunted flux qubits (CSFQs) connected by 40 rf-SQUID tunable couplers. Each CSFQ features state-of-the-art persistent current readout (https://arxiv.org/abs/2006.10817). Over 200 dedicated bias lines enable unprecedented control over annealing schedules. To achieve the required scale and signal density while maintaining high coherence, we leverage MIT Lincoln Laboratory’s 3-tier stack fabrication and 3D integration process. We show data validating key aspects of the novel modular architecture where control and readout circuitry traverse multiple tiers. We discuss initial qubit measurements, and the versatility of the architecture for algorithm and hardware prototyping.