Jenga-Krotov algorithm: Efficient compilation of multi-qubit gates for exchange-only qubits

Fuente: arXiv
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Main Authors: Wu, Jiahao, He, Guanjie, Zhuo, Wenyuan, Fu, Quan, Wang, Xin
Format: Preprint
Published: 2025
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author Wu, Jiahao
He, Guanjie
Zhuo, Wenyuan
Fu, Quan
Wang, Xin
author_facet Wu, Jiahao
He, Guanjie
Zhuo, Wenyuan
Fu, Quan
Wang, Xin
contents Exchange-only (EO) qubits, implemented in triple-quantum-dot systems, offer a compelling platform for scalable semiconductor-based quantum computing by enabling universal control through purely exchange interactions. While high-fidelity single- and two-qubit gates have been demonstrated, the synthesis of efficient multi-qubit operations-such as the Toffoli gate-remains a key bottleneck. Conventional gate decompositions into elementary operations lead to prohibitively long and error-prone pulse sequences, limiting practical deployment. In this work, we introduce a gradient-based optimization algorithm, Jenga-Krotov (JK), tailored to discover compact, high-fidelity EO gate sequences. Applying JK to the Toffoli gate, we reduce the number of required exchange unitaries from 216 (in direct decomposition) to 92, and compress the time steps required from 162 to 50, all while maintaining target fidelity. Under realistic noise, the accumulated gate error from our optimized sequence is an order of magnitude lower than that of conventional approaches. We have also applied the JK algorithm to other multi-qubit gates and algorithm. For the Fredkin gate, it reduces the number of time steps from 200 to 104 and the number of exchange unitaries from 276 to 172. For the quantum Fourier transform, it compresses the sequence from 180 to 80 time steps and from 237 to 202 exchange unitaries. These results demonstrate that the JK algorithm is a general and scalable strategy for multi-qubit gate synthesis in EO architectures, potentially facilitating realization of multi-qubit algorithms on semiconductor platforms.
format Preprint
id arxiv_https___arxiv_org_abs_2507_12448
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Jenga-Krotov algorithm: Efficient compilation of multi-qubit gates for exchange-only qubits
Wu, Jiahao
He, Guanjie
Zhuo, Wenyuan
Fu, Quan
Wang, Xin
Quantum Physics
Mesoscale and Nanoscale Physics
Computational Physics
Exchange-only (EO) qubits, implemented in triple-quantum-dot systems, offer a compelling platform for scalable semiconductor-based quantum computing by enabling universal control through purely exchange interactions. While high-fidelity single- and two-qubit gates have been demonstrated, the synthesis of efficient multi-qubit operations-such as the Toffoli gate-remains a key bottleneck. Conventional gate decompositions into elementary operations lead to prohibitively long and error-prone pulse sequences, limiting practical deployment. In this work, we introduce a gradient-based optimization algorithm, Jenga-Krotov (JK), tailored to discover compact, high-fidelity EO gate sequences. Applying JK to the Toffoli gate, we reduce the number of required exchange unitaries from 216 (in direct decomposition) to 92, and compress the time steps required from 162 to 50, all while maintaining target fidelity. Under realistic noise, the accumulated gate error from our optimized sequence is an order of magnitude lower than that of conventional approaches. We have also applied the JK algorithm to other multi-qubit gates and algorithm. For the Fredkin gate, it reduces the number of time steps from 200 to 104 and the number of exchange unitaries from 276 to 172. For the quantum Fourier transform, it compresses the sequence from 180 to 80 time steps and from 237 to 202 exchange unitaries. These results demonstrate that the JK algorithm is a general and scalable strategy for multi-qubit gate synthesis in EO architectures, potentially facilitating realization of multi-qubit algorithms on semiconductor platforms.
title Jenga-Krotov algorithm: Efficient compilation of multi-qubit gates for exchange-only qubits
topic Quantum Physics
Mesoscale and Nanoscale Physics
Computational Physics
url https://arxiv.org/abs/2507.12448