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[论文解读] Entangling ions with engineered light gradients

Tommaso Faorlin, Lorenz Panzl|arXiv (Cornell University)|Mar 8, 2026
Mechanical and Optical Resonators被引用 0
一句话总结

论文展示了一种用于囚禁离子系统的梯度场光位移纠缠门，利用横向结构化光抑制光谱拥挤，在多达12个离子链上实现>99.5% 保真度。

ABSTRACT

Spectral crowding of collective motional modes limits the fidelity of entangling interactions in trapped-ion quantum processors by inducing off-resonant coupling to spectator modes. We introduce a geometric-phase entangling interaction driven by a transverse, time-dependent structured-light force. By applying the force in a plane orthogonal to the optical propagation direction, we reduce the effects of spectral crowding while preserving single-ion addressing. The scheme is compatible with arbitrary qubit encodings, provided that the qubit states experience a differential AC Stark shift. We experimentally realise high-fidelity two-qubit gates with error rates below $5 imes10^{-3}$ in ion crystals containing up to 12 ions confined within a single potential well. These results establish gradient-field light-shift gates as a scalable approach to high-fidelity entangling generation in spectrally crowded trapped-ion systems.

研究动机与目标

  • 解决多离子纠缠门中的光谱拥挤和寄生耦合问题。
  • 引入由横向、结构化光驱动的几何相位纠缠相互作用。
  • 在保持单离子寻址的前提下，推出更长离子链上的纠缠操作。
  • 展示适用于可扩展囚禁离子体系的高保真两量子比特门。

提出的方法

  • 在TEM00模式和一个类似TEM10的横向模式中使用两个离共振的束，建立带横向梯度的状态相关光偶极力（ODF）。
  • 将梯度对准在与光传播方向正交的平面，以降低对观测轴向模式的耦合。
  • 在轴向COM模附近驱动运动，从而累积几何相位，产生σz⊗σz纠缠相互作用。
  • 以δ ≈ 2π·20 kHz的失谐和t_gate ≈ 220 μs实现四个相空间环，并通过朗姆巴式序列将相位映射到群体。
  • 基态量子比特通过标准光泵浦和置换态进行准备和测量，SPAM误差通过多门的指数衰减在保真度评估中得到考虑。
Figure 1: a) Sketch of the addressing system. Two beams in two spatial modes (orange and blue) are overlapped on a polarizing beam splitter cube, after being respectively deflected by AODs. The blue beam, initially propagating like a Gaussian beam, is converted to a TEM 10 spatial mode with a phase
Figure 1: a) Sketch of the addressing system. Two beams in two spatial modes (orange and blue) are overlapped on a polarizing beam splitter cube, after being respectively deflected by AODs. The blue beam, initially propagating like a Gaussian beam, is converted to a TEM 10 spatial mode with a phase

实验结果

研究问题

  • RQ1在多离子链中，通过工程化横向光梯度是否能抑制光谱拥挤，同时保持单离子寻址？
  • RQ2在最多12个离子链上，梯度场光位移门的保真度可达到多少，主导误差来源是什么？
  • RQ3在轴向与径向运动模式下纠缠性能有何差异？
  • RQ4通过梯度诱导的几何相位实现的σz⊗σz相互作用是否具备可扩展性以实现容错量子计算？

主要发现

Error mechanismInfidelity (×10^-4)AxialRadial
Spectator modes2.12.1742.4
Qubit T2 decoherence9.69.69.6
Motional decoherence8.78.718.8
RF pulses2.42.42.4
COM mode heating4.04.00.9
Qubit T1 decay1.11.11.1
Scattering (Rayleigh & Raman)1.21.21.2
Total29.129.1776.4
  • 在多达12个离子晶体中 demonstrated 高保真纠缠操作，保真度超过99.5%。
  • 在轴向（梯度）实现中，对观测寄生模式的耦合明显被抑制，相较径向模式方法表现更优。
  • 误差预算显示在径向配置中寄生模式误差占主导，但在轴向配置中被抑制；在所述案例中轴向门的总失效率为29.1×10^-4，而径向为776.4×10^-4。
  • 约220 μs 的门持续时间配合四个相空间环实现纠缠操作。
  • 通过重复门基准测试将SPAM误差与门误差分离，得到与容错相关的性能。
  • 该方案支持omg量子比特编码，且与可扩展的离子阱结构及潜在的芯片集成光学兼容。
Figure 2: a) Parity oscillations for a single gate on a two-ion crystal. Error bars are given by $\sqrt{(1-\mathrm{P}(\phi)^{2})/\mathrm{N}_{\mathrm{shots}}}$ . b) Residual spin motion entanglement. Each point is the result of $\mathrm{N}_{\mathrm{shots}}=200$ measurements of the Bell state at the c
Figure 2: a) Parity oscillations for a single gate on a two-ion crystal. Error bars are given by $\sqrt{(1-\mathrm{P}(\phi)^{2})/\mathrm{N}_{\mathrm{shots}}}$ . b) Residual spin motion entanglement. Each point is the result of $\mathrm{N}_{\mathrm{shots}}=200$ measurements of the Bell state at the c

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