Universal Weakly Fault-Tolerant Quantum Computation via Code Switching in the [[8,3,2]] Code

• URL: http://arxiv.org/abs/2603.15610v1
• Date: Mon, 16 Mar 2026 17:57:54 GMT
• Title: Universal Weakly Fault-Tolerant Quantum Computation via Code Switching in the [[8,3,2]] Code
• Abstract summary: We present a fault-tolerant code-switching protocol between two versions of the $[[8, 3, 2]]$ code.<n>One version supports weakly fault-tolerant single-qubit Clifford gates, while the other supports a logical $overlinemathrmCCZ$ gate.
• Score: 1.5024443617567174
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Code-switching offers a route to universal, fault-tolerant quantum computation by circumventing the limitation implied by the Eastin-Knill theorem against a universal transversal gate set within a single quantum code. Here, we present a fault-tolerant code-switching protocol between two versions of the $[[8, 3, 2]]$ code. One version supports weakly fault-tolerant single-qubit Clifford gates, while the other supports a logical $\overline{\mathrm{CCZ}}$ gate via transversal $T/T^\dagger$ together with logical $\overline{\mathrm{CZ}}$, $\overline{\mathrm{CNOT}}$, and $\overline{\mathrm{SWAP}}$ gates. Because both codes have distance 2, the protocol operates in a postselected, error-detecting regime: single faults lead to detectable outcomes, and accepted runs exhibit quadratic suppression of logical error rates. This yields a universal scheme for postselected fault-tolerant computation. We validate the protocol numerically through simulations of state preparation, code switching, and a three-logical-qubit implementation of Grover's search.

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