半导体量子点主要包括在真空中外延生长的自组织量子点和在溶液中采用化学方法合成的胶体量子点，由于量子限制效应所导致的分立能级结构使得它们通常被称为“人工原子”。和自然原子不同，半导体量子点的能级结构强烈依赖于其尺寸和形状，这样就提供了更为灵活的方法来控制固体材料中的光与材料的相互作用。近年来，许多类原子的量子光学现象(包括量子干涉、Rabi振荡和Mollow荧光)都已经在单个的自组织量子点中揭示出来。与此形成对比的是，上述所有的类原子量子光学特性目前还没有在单个的胶体量子点中观察得到。在本文中，我们将侧重于介绍我们科研组以及我们和别的科研组合作对单个自组织量子点的单量子态在光学探测和相干控制方面完成的一系列工作。对单个的胶体量子点，我们认为量子相干特性的测量和控制将在新近合成的非荧光闪烁或荧光闪烁得到抑制的材料体系中得以实现.
There are mainly two categories of semiconductor quantum dots (QDs): self-assembled QDs (SAQDs) that are epitaxially grown in ultrahigh vacuum and colloidal nanocrystal QDs (NCQDs) that are chemically synthesized in solution. QDs are often referred to as “artificial atoms” due to the discrete nature of their energy states predicted from the quantum confinement effect. Unlike natural atoms, the energy states of semiconductor QDs are size-tunable, thus providing a more flexible way to control the light-matter interactions in solid state. Indeed, a rich spectrum of atomic physics and quantum optics phenomena, including quantum interference, Rabi oscillations, and Mollow fluorescence, have been demonstrated in single SAQDs. Unfortunately, none of the above atomic-like properties has ever been observed in single colloidal NCQDs. Here, we focus on single SAQDs and review several experiments either performed in our group or done in collaboration with others on the optical detection and coherent manipulation of their single quantum states. For single NCQDs, we point out that coherent manipulation of their quantum states might be achieved in the near future from completely non-blinking or blinking suppressed NCQDs synthesized recently by several groups.
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