Superconducting qubit systems, one of the leading candidates for universal quantum computing, face scalability challenges such as frequency crowding, wiring complexity, and packaging problems. Distributed quantum computing offers a viable strategy for constructing larger quantum information processing systems. Yet, direct universal quantum gates between remote qubits—critical to distributed architectures—remain unrealized. Here, we demonstrate direct high-fidelity entangling gates between two remote superconducting quantum processors separated by a 30 cm distance, utilizing standing-wave modes in their connecting coaxial cable. We achieve cross-entropy benchmarking fidelities of $<span\; style="font-size:\; 16px;">(</span>$$\mathrm{<span\; style="font-size:\; 16px;">99.15</span>}<span\; style="font-size:\; 16px;">\pm </span>\mathrm{<span\; style="font-size:\; 16px;">0.02</span>}<span\; style="font-size:\; 16px;">)</span><span\; style="font-size:\; 16px;">\%</span>$ and $<span\; style="font-size:\; 16px;">(</span>\mathrm{<span\; style="font-size:\; 16px;">98.03</span>}<span\; style="font-size:\; 16px;">\pm </span>\mathrm{<span\; style="font-size:\; 16px;">0.04</span>}<span\; style="font-size:\; 16px;">)</span><span\; style="font-size:\; 16px;">\%</span>$ for the controlled-not and controlled-z gates, respectively, outperforming state transfer and feedback-based protocols in fidelity and efficiency. This advancement significantly enhances the prospect of universal distributed quantum information processing, which is the critical step toward future large-scale quantum systems.

Paper link: https://journals.aps.org/prl/abstract/10.1103/npr7-b7kq