Analytical two-pulse control of universal single-qubit gates in rotational ultracold NaCs molecules

• URL: http://arxiv.org/abs/2605.03461v1
• Date: Tue, 05 May 2026 07:48:17 GMT
• Title: Analytical two-pulse control of universal single-qubit gates in rotational ultracold NaCs molecules
• Abstract summary: We present an analytical framework for universal single-qubit gates using rotational states of ultracold NaCs molecules.<n>By encoding qubits in the lowest rotational energy levels, we employ a first-order Magnus expansion to derive closed-form unitary evolution.<n>Our method is also applicable to other molecules and physical platforms, offering a potential path to high-fidelity, scalable molecular quantum processors.
• Score: 5.906387038765238
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Complex control protocols and sensitivity to experimental imperfections have limited the practical implementation of quantum gate operations. Here, we present an analytical framework for universal single-qubit gates using rotational states of ultracold NaCs molecules. By encoding qubits in the lowest rotational energy levels, we employ a first-order Magnus expansion to derive closed-form unitary evolution from an optimized two-pulse sequence. This approach establishes precise amplitude and phase conditions for arbitrary single-qubit rotations, achieving gate fidelities above 0.9999 in numerical simulations. We further demonstrate that complex multi-gate sequences, including phase-locked operations, can be executed with minimal population leakage into auxiliary states. The time-dependent molecular orientation is shown to faithfully encode both the gate truth table and coherence dynamics, enabling practical gate tomography via weak-field polarization detection. Our analytical method is also applicable to other molecules and physical platforms, offering a potential path to high-fidelity, scalable molecular quantum processors.

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