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Quantum Skip Gates: Coherently Conditioned Subroutines in Iterative Quantum Algorithms

2025/05/31 by Kym Derriman, Derriman, Kym
Computer Science · #Advanced Algebra and Logic #FOS: Physical sciences #Logic, Reasoning, and Knowledge #Logic, programming, and type systems #Quantum Physics (quant-ph)

paper · pdf · doi:10.48550/arxiv.2506.00647

openalex publication_date 2025/05/31 · openalex created_date 2025/10/14 · openalex updated_date 2026/07/30

Abstract

The Quantum Skip Gate (QSG) is a unitary circuit primitive that coherently superposes the execution and omission of an expensive quantum subroutine based on the outcome of a cheaper preceding subroutine, without mid-circuit measurement or loss of coherence. By using a control qubit and an internal flag, QSG enables conditional quantum logic entirely within a unitary framework. We demonstrate QSG experimentally in a Grover-style search on IBM quantum hardware with four data qubits and three Grover iterations, where it reduces costly subroutine calls by 9 to 25 percent and achieves 31 to 61 percent higher success-per-oracle efficiency relative to a fixed-order baseline. Noise-model simulations further confirm and strengthen these gains, reaching improvements of up to 45 percent when using an optimized swap-out design. These results show that coherently conditioned subroutines provide practical resource management, significantly reducing runtime cost and noise accumulation in near-term quantum algorithms.

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