arXiv subjects

Ximo Wang

Publications and source records attributed to Ximo Wang.

4 recordsLinked to original sources

arXiv2026

Robust controlled-Z gate for Rydberg atoms based on level-crossing-free echoing rapid adiabatic passage

We propose a controlled-Z gate scheme for Rydberg atoms based on level-crossing-free echoing rapid adiabatic population transfer. We design antisymmetric Rabi frequency pulses and symmetric detuning pulses, enabling the system to completely avoid level-crossing points throughout the evolution, and the dynamical phase is naturally eliminated by the time-reversal symmetry of the double-pulse sequence. We incorporate dissipative effects through the Lindblad master equation. The numerical simulation yields a two-qubit CZ gate fidelity of 0.9999. When the Rabi-frequency fluctuation is within $\pm 2\%$, and the detuning offset is within $\pm 1\%$, the fidelity can still remain above 0.999. Under the same dissipative model, the three-qubit CCZ gate achieves a fidelity of 0.999. When a single-parameter fluctuation does not exceed $\pm 3\%$, the fidelity is always higher than 0.997. Our scheme requires no laser phase jumps or fast switching operations. The zero-area pulse structure suppresses first-order intensity noise, and the symmetric double-pulse sequence avoids spatially resolved laser switching, making it suitable for parallel gate operations in large-scale neutral-atom arrays.

quant-ph↗

arXiv2026

High-fidelity multiqubit gates with Rydberg atoms via level-crossing-free Rapid adiabatic passage

We propose a rapid adiabatic passage (RAP) scheme based on level-crossing-free pulses for deterministic generation of multiqubit entangled states in Rydberg atom systems. Unlike conventional RAP protocols that rely on level crossings, our approach uses an antisymmetric Rabi frequency and an even-symmetric detuning, enabling robust population transfer without passing through any level crossing. By exploiting the Rydberg blockade effect, the protocol prepares entangled states directly from an initial product state. Specifically, two sequential RAP pulses separated by a pi_g pulse generate two-qubit Bell states, three-qubit W states, four-qubit GHZ states, and six-qubit honeycomb W states. Numerical simulations show that the fidelities exceed 0.9997 for the Bell and three-qubit W states, reach 0.997 for the four-qubit GHZ state, and surpass 0.9995 for the six-qubit honeycomb W state. The scheme demonstrates excellent robustness against pulse parameter fluctuations, with fidelities remaining above 0.99 under +/-5% parameter variations. This work provides a simple, efficient, and robust method for entangled-state preparation in neutral-atom quantum information processing.

quant-ph↗

arXiv2025

Strongly Coupled Continuous Time Crystal

Time crystals are classified into discrete time crystals and continuous time crystals based on whether they spontaneously break time-translation symmetry. Continuous-time crystals do not require external driving. By introducing AdS/CFT duality to time crystals, we derive their thermodynamic limit and find that in strongly correlated many-body systems such as a 3D optical lattice(ions or tweezer in supplemental materials), cooperative many-body tunneling enables time crystals to oscillate spontaneously. In strongly correlated quantum systems driven by many-body cooperative tunneling, we discover a universal scaling law governing the time-crystalline phase transition at a critical temperature.

quant-ph↗

arXiv2025

Geometric Quantum Gates of Non-closed Paths Under Counterdiabatic Driving

Non-adiabatic and non-closed evolutionary paths play a significant role in the fidelity of quantum gates. We propose a high-fidelity quantum control framework based on the quasi-topological number ($\nu_{\text{qua}}$), which extends the traditional Chern number to characterize geometric responses in non-closed paths. By introducing a counterdiabatic gauge potential (AGP) that dynamically suppresses non-adiabatic transitions and reconstructs path curvature, we demonstrate that $\nu_{\text{qua}}$ -a relative homotopy invariant of compact manifolds in parameter space-quantifies the robustness of geometric phases during open-path quantum evolution. This integer invariant ensures gauge-invariant suppression of decoherence errors arising from dynamical phase coupling. By introducing nonlinear parametric ring paths, we address the defects caused by intermediate states in the Rydberg atomic system. Numerical simulations in the Kitaev superconducting chain and 2D transverse-field Ising model confirm that our protocol achieves quantum gate fidelity exceeding $\mathcal{F} > 0.9999$. We bridges geometric quantum control with topological protection, offering a universal approach to noise-resistant quantum computing.

quant-ph↗