Opt Express. 2023 Apr 24;31(9):13970-13980. doi: 10.1364/OE.481256.
One of the critical elements in the realization of the quantum internet are deterministic two-photon gates. This CZ photonic gate also completes a set of universal gates for all-optical quantum information processing. This article discusses an approach to realize a high fidelity CZ photonic gate by storing both control and target photons within an atomic ensemble using non-Rydberg electromagnetically induced transparency (EIT) followed by a fast, single-step Rydberg excitation with global lasers. The proposed scheme operates by relative intensity modulation of two lasers used in Rydberg excitation. Circumventing the conventional π-gap-π schemes, the proposed operation features continuous laser protection of the Rydberg atoms from the environment noise. The complete spatial overlap of stored photons inside the blockade radius optimizes the optical depth and simplifies the experiment. The coherent operation here is performed in the region that was dissipative in the previous Rydberg EIT schemes. Encountering the main imperfection sources, i.e., the spontaneous emission of the Rydberg and intermediate levels, population rotation errors, Doppler broadening of the transition lines, storage/retrieval efficiency, and atomic thermal motion induced decoherence, this article concludes that with realistic experimental parameters 99.7% fidelity is achievable.
实现量子互联网的关键因素之一是确定性双光子门。这个 CZ 光子门也完成了一套用于全光量子信息处理的通用门。本文讨论了一种通过使用非里德堡电磁感应透明（EIT）在原子系综中存储控制和目标光子，然后使用全局激光器进行快速、单步里德堡激发，来实现高保真 CZ 光子门的方法。所提出的方案通过在里德堡激发中使用的两个激光的相对强度调制来操作。绕过传统的π隙-π方案，所提出的操作具有连续激光保护里德堡原子免受环境噪声的影响。存储光子在阻塞半径内的完全空间重叠优化了光学深度并简化了实验。这里的相干操作是在之前的里德堡 EIT 方案中耗散的区域中进行的。在遇到主要的不完美源，即里德堡和中间能级的自发发射、粒子数旋转误差、跃迁线的多普勒展宽、存储/检索效率以及原子热运动诱导的退相干后，本文得出结论，使用现实的实验参数可以实现 99.7%的保真度。
