Publications Zhongda ZENG

2025

Article

• Z. Zeng, G. Giudici, H. Pichler Quantum dimer models with Rydberg gadgets, Phys. Rev. Research 7 L012006 (2025-01-09), http://dx.doi.org/10.1103/PhysRevResearch.7.L012006 doi:10.1103/PhysRevResearch.7.L012006 (ID: 721245) Toggle Abstract
  The Rydberg blockade mechanism is an important ingredient in quantum simulators based on neutral atom arrays. It enables the emergence of a rich variety of quantum phases of matter, such as topological spin liquids. The typically isotropic nature of the blockade effect, however, restricts the range of natively accessible models and quantum states. In this work, we propose a method to systematically overcome this limitation, by developing gadgets, i.e., specific arrangements of atoms, that transform the underlying Rydberg blockade into more general constraints. We apply this technique to realize dimer models on square and triangular geometries. In these setups, we study the role of the quantum fluctuations induced by a coherent drive of the atoms and find signatures of U(1) and Z2 quantum spin liquid states in the respective ground states. Finally, we show that these states can be dynamically prepared with high fidelity, paving the way for the quantum simulation of a broader class of constrained models and topological matter in experiments with Rydberg atom arrays.

Preprints

• A. Senoo, A. Baumgärtner, J. W. Lis, G. M. Vaidya, Z. Zeng, G. Giudici, H. Pichler, A. Kaufman High-fidelity entanglement and coherent multi-qubit mapping in an atom array, (2025-06-16), arXiv:2506.13632 arXiv:2506.13632 (ID: 721484) Toggle Abstract
  Neutral atoms in optical tweezer arrays possess broad applicability for quantum information science, in computing, simulation, and metrology. Among atomic species, Ytterbium-171 is unique as it hosts multiple qubits, each of which is impactful for these distinct applications. Consequently, this atom is an ideal candidate to bridge multiple disciplines, which, more broadly, has been an increasingly effective strategy within the field of quantum science. Realizing the full potential of this synergy requires high-fidelity generation and transfer of many-particle entanglement between these distinct qubit degrees of freedom, and thus between these distinct applications. Here we demonstrate the creation and coherent mapping of entangled quantum states across multiple qubits in Ytterbium-171 tweezer arrays. We map entangled states onto the optical clock qubit from the nuclear spin qubit or the Rydberg qubit. We coherently transfer up to 20 atoms of a -ordered Greenberger-Horne-Zeilinger (GHZ) state from the interacting Rydberg manifold to the metastable nuclear spin manifold. The many-body state is generated via a novel disorder-robust pulse in a two-dimensional ladder geometry. We further find that clock-qubit-based spin detection applied to Rydberg and nuclear spin qubits facilitates atom-loss-detectable qubit measurements and Rydberg decay detection. This enables mid-circuit and delayed erasure detection, yielding an error-detected two-qubit gate fidelity of in the metastable qubits as well as enhanced GHZ state fidelities in analog preparation. These results establish a versatile architecture that advances multiple fields of quantum information science while also establishing bridges between them.
• Z. Zeng, G. Giudici, A. Senoo, A. Baumgärtner, A. Kaufman, H. Pichler Adiabatic echo protocols for robust quantum many-body state preparation, (2025-06-13), arXiv:2506.12138 arXiv:2506.12138 (ID: 721485) Toggle Abstract
  Entangled many-body states are a key resource for quantum technologies. Yet their preparation through analog control of interacting quantum systems is often hindered by experimental imperfections. Here, we introduce the adiabatic echo protocol, a general approach to state preparation designed to suppress the effect of static perturbations. We provide an analytical understanding of its robustness in terms of dynamically engineered destructive interference. By applying quantum optimal control methods, we demonstrate that such a protocol emerges naturally in a variety of settings, without requiring assumptions on the form of the control fields. Examples include Greenberger-Horne-Zeilinger state preparation in Ising spin chains and two-dimensional Rydberg atom arrays, as well as the generation of quantum spin liquid states in frustrated Rydberg lattices. Our results highlight the broad applicability of this protocol, providing a practical framework for reliable many-body state preparation in present-day quantum platforms.

2024

Preprint

• L. Bombieri, Z. Zeng, R. Tricarico, R. Lin, S. Notarnicola, M. Cain, M. Lukin, H. Pichler Quantum adiabatic optimization with Rydberg arrays: localization phenomena and encoding strategies, (2024-11-07), arXiv:2411.04645 arXiv:2411.04645 (ID: 721280) Toggle Abstract
  We study the quantum dynamics of the encoding scheme proposed in [Nguyen et al., PRX Quantum 4, 010316 (2023)], which encodes optimization problems on graphs with arbitrary connectivity into Rydberg atom arrays. Here, a graph vertex is represented by a wire of atoms, and the (crossing) crossing-with-edge gadget is placed at the intersection of two wires to (de)couple their degrees of freedom and reproduce the graph connectivity. We consider the fundamental geometry of two vertex-wires intersecting via a single gadget and look at minimum gap scaling with system size along adiabatic protocols. We find that both polynomial and exponential scaling are possible and, by means of perturbation theory, we relate the exponential closing of the minimum gap to an unfavorable localization of the ground-state wavefunction. Then, on the QuEra Aquila neutral atom machine, we observe such localization and its effect on the success probability of finding the correct solution to the encoded optimization problem. Finally, we propose possible strategies to avoid this quantum bottleneck, leading to an exponential improvement in the adiabatic performance.