[论文解读] High-efficiency single-photon source above the loss-tolerant threshold for efficient linear optical quantum computing

Xing Ding, Yong-Peng Guo+14 more|arXiv (Cornell University)|Nov 14, 2023

Photonic and Optical Devices被引用 20

一句话总结

本文报道了一种在可调开式微腔中共振激发的量子点单光子源，实现端到端系统效率高于容错阈值，具有高纯度和不可区分性。

ABSTRACT

Photon loss is the biggest enemy for scalable photonic quantum information processing. This problem can be tackled by using quantum error correction, provided that the overall photon loss is below a threshold of 1/3. However, all reported on-demand and indistinguishable single-photon sources still fall short of this threshold. Here, by using tailor shaped laser pulse excitation on a high-quantum efficiency single quantum dot deterministically coupled to a tunable open microcavity, we demonstrate a high-performance source with a single-photon purity of 0.9795(6), photon indistinguishability of 0.9856(13), and an overall system efficiency of 0.712(18), simultaneously. This source for the first time reaches the efficiency threshold for scalable photonic quantum computing. With this source, we further demonstrate 1.89(14) dB intensity squeezing, and consecutive 40-photon events with 1.67 mHz count rate.

研究动机与目标

• 通过高效单光子源克服光子损耗，推动可扩展的光量子计算。
• 演示一个按需单光子源，能够同时实现高纯度、高不可区分性和高整体效率。
• 证明所达到的效率超越容错线性光量子计算的损耗容忍阈值。

提出的方法

• 使用定制形状的激光脉冲激发，使单个量子点在可调开式微腔中的确定性耦合下实现共振驱动。
• 使用模分裂腔以实现偏振选择性激发与发射收集。
• 实现 4f 脉冲整形以收窄激发带宽并最大化相干量子点-腔耦合。
• 用 Hanbury Brown and Twiss (HBT) 测量纯度，用非后选的 Hong-Ou-Mandel (HOM) 干涉测量不可区分性，并对多光子事件进行校正。
• 从端到端计数中量化系统效率，考虑探测器效率和重复率，达到 0.712(18) 的基准。

Figure 1: The design of the QDs in a fully tunable open-cavity setup. The top concave cavity mirror is mounted on a stack of three piezo nano-positioners. The bottom part, including 30 pairs DBR and QD layer, is mounted on a stack of three nano-positioners (XYZ) and two tilt stages ( $\Theta,\Phi$ )

实验结果

研究问题

• RQ1 量子点单光子源是否能同时实现高纯度、高不可区分性，以及端到端效率高于损耗容忍阈值？
• RQ2 开式腔的可调性和脉冲整形如何影响共振激发效率和光子统计？
• RQ3 对于近变换极限、高效源，时延对不可区分性的极限是什么？

主要发现

• 单光子纯度为 0.9795(6)。
• 不可区分性为 0.9856(13)。
• 系统效率为 0.712(18)。
• 在 π 脉冲激发下的强度挤压为 1.89(14) dB。
• 在 1.67 mHz 计数率下观察到 40 个连续光子事件。
• 致力于超越可扩展光子量子计算的损耗容忍阈值。

Figure 2: High-efficiency single-photon source (SPS) under shape-optimized pulse excitation. (a) Excitation scheme of a polarized single-photon source in a mode-splitting cavity. (b) Deterministic generation of polarized single photons under a series of pulse excitations with different pulse widths.