Modular Quantum Processor with an All-to-All Reconfigurable Router

• Published in: Physical review. X Vol. 14; no. 4; p. 041030
• Main Authors: Wu, Xuntao, Yan, Haoxiong, Andersson, Gustav, Anferov, Alexander, Chou, Ming-Han, Conner, Christopher R., Grebel, Joel, Joshi, Yash J., Li, Shiheng, Miller, Jacob M., Povey, Rhys G., Qiao, Hong, Cleland, Andrew N.
• Format: Journal Article
• Language: English
• Published: United States American Physical Society 01.11.2024
• ISSN: 2160-3308; 2160-3308
• DOI: 10.1103/PhysRevX.14.041030

Superconducting qubits provide a promising approach to large-scale fault-tolerant quantum computing. However, qubit connectivity on a planar surface is typically restricted to only a few neighboring qubits. Achieving longer-range and more flexible connectivity, which is particularly appealing in light of recent developments in error-correcting codes, however, usually involves complex multilayer packaging and external cabling, which is resource intensive and can impose fidelity limitations. Here, we propose and realize a high-speed on-chip quantum processor that supports reconfigurable all-to-all coupling with a large on-off ratio. We implement the design in a four-node quantum processor, built with a modular design comprising a wiring substrate coupled to two separate qubit-bearing substrates, each including two single-qubit nodes. We use this device to demonstrate reconfigurable controlled- Z gates across all qubit pairs, with a benchmarked average fidelity of 96.00 % ± 0.08 % and best fidelity of 97.14 % ± 0.07 % , limited mainly by dephasing in the qubits. We also generate multiqubit entanglement, distributed across the separate modules, demonstrating GHZ-3 and GHZ-4 states with fidelities of 88.15 % ± 0.24 % and 75.18 % ± 0.11 % , respectively. This approach promises efficient scaling to larger-scale quantum circuits and offers a pathway for implementing quantum algorithms and error-correction schemes that benefit from enhanced qubit connectivity. Published by the American Physical Society 2024