Synchronized dynamics of quantum dot (QD) ensembles are essential for generating ultrafast and giant optical responses beyond those of individual QDs. Increasing the strength of the direct electronic coupling between QDs is a key strategy for the realization of cooperative quantum phenomena. Here, we observe a quantum cooperative effect on nonlinear photocurrents caused by the coherent electronic coupling in semiconductor QD solids. We measure quantum interference signals cooperatively generated in QD solids. We control the inter-QD distance with atomic precision using bidentate ligands that strongly link the QDs. The harmonic quantum interference signals are strongly enhanced when shortening the molecular length of the ligand. Furthermore, we clarify that the coherence length of multiexcitons extends to neighbouring QDs. This finding is direct evidence that multiexciton coherent tunnelling assists the ultrafast exciton delocalization. Cooperative enhancement in QD solids may find application in advanced quantum optoelectronics.

量子点 (QD) 整体的同步动力学对于产生超越单个 QD 的超快和巨大的光学响应至关重要。增加量子点之间直接电子耦合的强度是实现协同量子现象的关键策略。在这里，我们观察到半导体量子点固体中相干电子耦合引起的非线性光电流的量子协同效应。我们测量量子点固体中协同产生的量子干涉信号。我们使用紧密连接量子点的双齿配体以原子精度控制量子点间的距离。当缩短配体的分子长度时，谐波量子干涉信号强烈增强。此外，我们阐明多激子的相干长度延伸到相邻的量子点。这一发现是多激子相干隧道效应有助于超快激子离域的直接证据。量子点固体的协同增强可能会在先进的量子光电子学中得到应用。