Modular quantum processor with an all-to-all reconfigurable router

TL;DR

This paper presents a modular superconducting quantum processor with reconfigurable all-to-all connectivity, enabling high-fidelity multi-qubit operations and entanglement distribution across modules, promising scalable quantum computing.

Contribution

The authors design and demonstrate a modular, reconfigurable all-to-all coupling architecture in a superconducting quantum processor, achieving high-fidelity gates and entanglement across modules.

Findings

Reconfigurable controlled-Z gates with 96% average fidelity.

Generation of GHZ-3 and GHZ-4 states with high fidelity.

Scalable modular design for enhanced qubit connectivity.

Abstract

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 multi-layer 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 $96.00\%\pm0.08\%$ and best fidelity of $97.14\%\pm0.07\%$, limited mainly by dephasing in the qubits. We also generate multi-qubit entanglement, distributed across the separate modules, demonstrating GHZ-3 and GHZ-4 states with fidelities of $88.15\%\pm0.24\%$ and $75.18\%\pm0.11\%$, 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.