Abstract
Assembling future large-scale quantum computers out of smaller, specialized modules promises to simplify a number of formidable science and engineering challenges. One of the primary challenges in developing a modular architecture is in engineering high fidelity, low-latency quantum interconnects between modules. Here we demonstrate a modular solid state architecture with deterministic inter-module coupling between four physically separate, interchangeable superconducting qubit integrated circuits, achieving two-qubit gate fidelities as high as 99.1 ± 0.5% and 98.3 ± 0.3% for iSWAP and CZ entangling gates, respectively. The quality of the inter-module entanglement is further confirmed by a demonstration of Bell-inequality violation for disjoint pairs of entangled qubits across the four separate silicon dies. Having proven out the fundamental building blocks, this work provides the technological foundations for a modular quantum processor: technology which will accelerate near-term experimental efforts and open up new paths to the fault-tolerant era for solid state qubit architectures.
Highlights
Progress in quantum operations over multi-node networks could enable modular architectures spanning distances from the nanometer to the kilometer scale[1,2,3,4,5]
The device, which consists of four eight-qubit integrated circuits (QuICs) fabricated on individual dies and flip-chip bonded to a larger carrier chip, achieves coupling rates and entanglement quality approaching the state-of-the-art in intra-chip coupling
The carrier chip assumes a similar role to the chip multiprocessor in a classical multi-core processor while providing microwave shielding, circuitry to interface between the individual QuICs and signal routing for the device I/O
Summary
Progress in quantum operations over multi-node networks could enable modular architectures spanning distances from the nanometer to the kilometer scale[1,2,3,4,5]. In the context of superconducting qubit based processors, none of these methods are likely to outperform local gates between qubits, which can achieve coupling rates in the tens of MHz and fidelities reaching 99.9%19–23. Modules consisting of closely spaced and directly coupled separate physical dies retain many of the benefits of distributed modular architectures without the challenge of remote entanglement. Mastering 3D integration and modular solid state architectures has been a long-standing objective[29,30,31]. We demonstrate a modular superconducting qubit device with direct coupling between physical modules. The device, which consists of four eight-qubit integrated circuits (QuICs) fabricated on individual dies and flip-chip bonded to a larger carrier chip, achieves coupling rates and entanglement quality approaching the state-of-the-art in intra-chip coupling
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