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Physical Review A

Enhancing ground-state interaction strength of neutral atoms via Floquet stroboscopic dynamics

Yue Wei, M. Artoni, Giuseppe Carlo La Rocca, Jin‐Hui Wu, Xiao‐Qiang Shao

Published Feb 25, 2026• 3 citations
Publisher

Abstract

Neutral-atom systems are promising platforms for quantum simulation and computation, owing to their long coherence times. However, their intrinsically weak ground-state interactions pose a major limitation to the advancement of scalable quantum simulation and computation. To address this challenge, we propose an approach to enhancing the ground-state interaction strength of neutral atoms via Floquet modulation of a Rydberg atomic ensemble. Each Floquet period consists of ground-state coupling followed by a pulse driving the transition from the ground state to the Rydberg state. Theoretical analysis and numerical simulations demonstrate that after a defined evolution time, neutral atoms within Rydberg ensembles can collectively form a W state in the ground-state manifold. Even when the Rydberg interaction strength is far below the blockade regime, the fidelity remains remarkably high. Finally, we analyze the application of this scheme in the preparation of single-photon sources. In general, our proposed mechanism offers an efficient and highly controllable method for quantum state preparation within the Rydberg atomic ensembles, significantly enhancing the accuracy and stability of quantum state engineering while providing a well-controlled quantum environment for single-photon generation.

DOI
10.1103/7zjs-73qm

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Neutral atom systems are promising platforms for quantum simulation and computation, owing to their long coherence times. However, their intrinsically weak ground-state interactions pose a major limitation to the advancement of scalable quantum simulation and computation. To address this challenge, we propose an approach to enhancing the ground-state interaction strength of neutral atoms via Floquet modulation of a Rydberg atomic ensemble. Each Floquet period consists of ground-state coupling followed by a pulse driving the transition from the ground state to the Rydberg state. Theoretical analysis and numerical simulations demonstrate that after a defined evolution time, neutral atoms within Rydberg ensembles can collectively form a $W$ state in the ground-state manifold. Even when the Rydberg interaction strength is far below the blockade regime, the fidelity remains remarkably high. Finally, we analyze the application of this scheme in the preparation of single-photon sources. In general, our proposed mechanism offers an efficient and highly controllable method for quantum state preparation within the Rydberg atomic ensembles, significantly enhancing the accuracy and stability of quantum state engineering while providing a well-controlled quantum environment for single-photon generation.

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Neutral-atom systems are promising platforms for quantum simulation and computation, owing to their long coherence times. However, their intrinsically weak ground-state interactions pose a major limitation to the advancement of scalable quantum simulation and computation. To address this challenge, we propose an approach to enhancing the ground-state interaction strength of neutral atoms via Floquet modulation of a Rydberg atomic ensemble. Each Floquet period consists of ground-state coupling followed by a pulse driving the transition from the ground state to the Rydberg state. Theoretical analysis and numerical simulations demonstrate that after a defined evolution time, neutral atoms within Rydberg ensembles can collectively form a W state in the ground-state manifold. Even when the Rydberg interaction strength is far below the blockade regime, the fidelity remains remarkably high. Finally, we analyze the application of this scheme in the preparation of single-photon sources. In general, our proposed mechanism offers an efficient and highly controllable method for quantum state preparation within the Rydberg atomic ensembles, significantly enhancing the accuracy and stability of quantum state engineering while providing a well-controlled quantum environment for single-photon generation.
Neutral atom systems are promising platforms for quantum simulation and computation, owing to their long coherence times. However, their intrinsically weak ground-state interactions pose a major limitation to the advancement of scalable quantum simulation and computation. To address this challenge, we propose an approach to enhancing the ground-state interaction strength of neutral atoms via Floquet modulation of a Rydberg atomic ensemble. Each Floquet period consists of ground-state coupling followed by a pulse driving the transition from the ground state to the Rydberg state. Theoretical analysis and numerical simulations demonstrate that after a defined evolution time, neutral atoms within Rydberg ensembles can collectively form a WWW state in the ground-state manifold. Even when the Rydberg interaction strength is far below the blockade regime, the fidelity remains remarkably high. Finally, we analyze the application of this scheme in the preparation of single-photon sources. In general, our proposed mechanism offers an efficient and highly controllable method for quantum state preparation within the Rydberg atomic ensembles, significantly enhancing the accuracy and stability of quantum state engineering while providing a well-controlled quantum environment for single-photon generation.
This thesis reports progress towards using hyperfine-encoded neutral atomic ensembles for quantum information applications. Ensemble qubits are alternative building blocks to process quantum information, while circumventing the challenges preparing a low-entropy single-atom qubit register. While ensemble approach inherits the single-atom quantum gate protocols, cooperative atom-light interaction makes it favorable platform to implement atom-photon interface, such as quantum memory. We have demonstrated semi-deterministic preparation of W-state, which we use as an ensemble qubit. Observed 50–60% preparation fidelity shows discrepancy to expected > 80% fidelity including known imperfections. We suspect Ground-Rydberg and Rydberg-Rydberg molecular interactions within the ensemble modify the dynamics. State tomography and Ramsey experiment clearly identified that majority of constituents in an ensemble are indeed entangled. We report the first measurement of W-state coherence time as 2.6ms for 7.6 atoms, which is long enough to perform 2600 Rydberg-mediated quantum gate operations. The first demonstration of Rydberg blockade between two ensembles happened in the same apparatus. We observe blockade fidelity of 0.89 (uncorrected) and near unity when post-selected on successful N = 1 Fock state preparation of Control ensemble. For weakly blockaded cases, Target ensemble remained as a perturber inhibiting Control ensemble from de-excitation. We discuss the efficacy of optical lattice insertion to suppress molecular interactions that might have been affecting the Rydberg dynamics. High fidelity, parallel, low loss fluorescence detection of hyperfine ground state of rubidium atoms is presented. Enforced cycling transition scattering minimally alters the internal states. We achieve mean state detection fidelity of 97% (uncorrected) and 98.7% (SPAM error corrected), with atom loss rate < 2% and hyperfine-changing rate < 2%. This scalable technique is also compatible with ensemble qubits and error correcting schemes. Technical developments on apparatus, lasers, supporting hardware and software are discussed. Automatic beam alignment system is implemented to correct long term drift of tightly focused addressing beams. Achieved pointing stability of 60 nm. Two home-made, high performing, cavity-enhanced frequency doubling systems were constructed to meet experimental demand. We observe 960/480 system output as high as 180 mW with 600 mW fundamental, and 1540/770 system output as high as 13.97 W from 19 W fundamental.
Abstract We propose new applications of Floquet theory in Rydberg atoms for constructing quantum entangling gates in atomic ground-state manifolds. By dynamically periodically modulating the Rabi frequencies of transitions between ground and Rydberg states of atoms, error-resilient two-qubit entangling gates can be implemented in the regime of Rydberg blockade. According to different degrees of Floquet theory utilization, the fidelity of the resulting controlled gates surpasses that of the original reference, and it exhibits high robustness against Rabi error in two qubits and detuning error in the control qubit. Our method only uses encoding in the ground states, and compared to the original scheme using Rydberg state for encoding, it is less susceptible to environmental interference, making it more practical to implement. Therefore, our approach may have broader applications or potential for further expansion of geometric quantum computation with neutral atoms.
Neutral atom arrays driven into Rydberg states constitute a promising approach for realizing programmable quantum systems. Enabled by strong interactions associated with Rydberg blockade, they allow for simulation of complex spin models and quantum dynamics. We introduce a new Floquet engineering technique for systems in the blockade regime that provides control over novel forms of interactions and entanglement dynamics in such systems. Our approach is based on time-dependent control of Rydberg laser detuning and leverages perturbations around periodic many-body trajectories as resources for operator spreading. These time-evolved operators are utilized as a basis for engineering interactions in the effective Hamiltonian describing the stroboscopic evolution. As an example, we show how our method can be used to engineer strong spin exchange, consistent with the blockade, in a one-dimensional chain, enabling the exploration of gapless Luttinger liquid phases. In addition, we demonstrate that combining gapless excitations with Rydberg blockade can lead to dynamic generation of large-scale multipartite entanglement. Experimental feasibility and possible generalizations are discussed.
Abstract We theoretically propose a protocol for coherent quantum state control in a short periodically driven Rydberg atom array. This Floquet engineering effectively suppresses the Rabi coupling and further reshapes Rydberg–Rydberg interactions, enabling precise control of Rydberg dynamics, including population trapping and blockade dynamics. This capability permits the coherent manipulation of targeted quantum states, such as the population-trapping ground state and entangled states with single or double excitations. A key finding is the robustness of these dynamics against variations in the Rydberg atom interaction, allowing for reliable control even in weak interaction regimes. Floquet spectral analysis further reveals that the stability — and eventual breakdown — of the frozen ground state is fundamentally governed by the splitting, convergence, and spacing of quasienergy levels. Moreover, a systematic analysis of parameter dependence identifies precise operational ranges for quantum state control. These results establish a practical framework for Floquet-engineered quantum manipulation, with promising prospects for quantum information processing applications.
The Rydberg blockade is a key ingredient for entangling atoms in arrays. However, it requires atoms to be spaced well within the blockade radius, which limits the range of local quantum gates. Here we break this constraint using Floquet frequency modulation, with which we demonstrate Rydberg-blockade entanglement beyond the traditional blockade radius and show how the enlarged entanglement range improves qubit connectivity in a neutral atom array. Further, we find that the coherence of entangled states can be extended under Floquet frequency modulation. Finally, we realize Rydberg anti-blockade states for two sodium Rydberg atoms within the blockade radius. Such Rydberg anti-blockade states for atoms at close range enables the robust preparation of strongly-interacting, long-lived Rydberg states, yet their steady-state population cannot be achieved with only the conventional static drive. Our work transforms between the paradigmatic regimes of Rydberg blockade versus anti-blockade and paves the way for realizing more connected, coherent, and tunable neutral atom quantum processors with a single approach.