Optimal Quantum-Circuit Synthesis and Implementation of General Unitaries with Parallelized Bitstring-Conditioned Rotations
Abstract
We theoretically introduce a quantum-circuit synthesis protocol to realize any n-qubit transformation U∈ U(2n), up to a diagonal. The resulting circuit is directly native to and optimal in gate count and depth for systems where bitstring-conditioned rotations with tunable angle and axis, C(n−1)R(θ,ϕ), form the set of native operations. Subsequently, we suggest how this protocol can be implemented in a few-mode superconducting circuit, and experimentally demonstrate the method for the smallest nontrivial case, i.e., for two qubits. We report an average gate fidelity of 97.6 % for Haar-random two-qubit unitaries up to phase shifts in the computational basis. Importantly, these results suggest that multimode devices, such as those in the multimon or multiunimon families may become competitive with qubit-array networks for general-unitary implementations for qubit counts as low as three.
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BibTeX
@misc{suominen2026optimal,
title = {{Optimal Quantum-Circuit Synthesis and Implementation of General Unitaries with Parallelized Bitstring-Conditioned Rotations}},
author = {Heikki Suominen and Suman Kundu and Heidi Kivijärvi and Sasu Tuohino and Mikko Tuokkola and Eemeli Forsbom and Madhavi Chand and Vasilii Vadimov and R. Vijay and Mikko Möttönen},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28057},
eprint = {2610.28057},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28057},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Optimal Quantum-Circuit Synthesis and Implementation of General Unitaries with Parallelized Bitstring-Conditioned Rotations
AU - Heikki Suominen
AU - Suman Kundu
AU - Heidi Kivijärvi
AU - Sasu Tuohino
AU - Mikko Tuokkola
AU - Eemeli Forsbom
AU - Madhavi Chand
AU - Vasilii Vadimov
AU - R. Vijay
AU - Mikko Möttönen
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28057
UR - https://arxiv.org/abs/2610.28057
AB - We theoretically introduce a quantum-circuit synthesis protocol to realize any n-qubit transformation U∈ U(2^n), up to a diagonal. The resulting circuit is directly native to and optimal in gate count and depth for systems where bitstring-conditioned rotations with tunable angle and axis, C^(n−1)R(θ,ϕ), form the set of native operations. Subsequently, we suggest how this protocol can be implemented in a few-mode superconducting circuit, and experimentally demonstrate the method for the smallest nontrivial case, i.e., for two qubits. We report an average gate fidelity of 97.6 % for Haar-random two-qubit unitaries up to phase shifts in the computational basis. Importantly, these results suggest that multimode devices, such as those in the multimon or multiunimon families may become competitive with qubit-array networks for general-unitary implementations for qubit counts as low as three.
ER -