Genuine Multipartite Entanglement between Logical Qubits via Cross-Code Lattice Surgery

• URL: http://arxiv.org/abs/2607.04227v1
• Date: Sun, 05 Jul 2026 11:01:11 GMT
• Title: Genuine Multipartite Entanglement between Logical Qubits via Cross-Code Lattice Surgery
• Abstract summary: We report on the generation and certification of genuine logical multipartite entanglement in a trapped-ion quantum processor.<n>The gate set is accessed via lattice surgery across two different codes.<n>These demonstrations showcase the core building blocks of an architecture for fault-tolerant quantum computation.
• Score: 0.34286994433699663
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Universal quantum computers are expected to generate arbitrary complex quantum states of logical qubits encoded in many physical qubits. This capability hinges on a fault-tolerantly implemented universal gate set, which no single quantum error-correction code admits transversally but which becomes accessible by joining complementary codes via lattice surgery. Here we report on the experimental generation and certification of logical genuine multipartite entanglement in a trapped-ion quantum processor using a transversally implemented universal logical gate set. The gate set is accessed via lattice surgery across two different codes and comprises a Hadamard gate on a four-qubit surface code and a doubly controlled Pauli-$Z$ ($\overline{\mathrm{CCZ}}$) gate on an eight-qubit 3D colour code. To showcase this lattice-surgery toolbox, we generate both stabiliser (Greenberger-Horne-Zeilinger) and non-stabiliser ($|\overline{\mathrm{CCZ}}\rangle$) states of three logical qubits and verify their genuine multipartite entanglement--a form of correlation beyond statistical mixtures of bipartite entanglement across any bipartition. We further use these cross-code primitives to demonstrate arbitrary rotations of single logical qubits via a $\overline{\mathrm{CCZ}}$-based resource gadget accessing the full universal gate set through lattice surgery. Together, these demonstrations showcase the core building blocks of an architecture for fault-tolerant quantum computation and its ability to generate complex logical quantum states.

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