Semiconductor quantum dots (QDs) are nanocrystals with atom-like delta function density of states and discrete energy levels. Advancements in fabrication led to record QD homogeneity and implementation in semiconductor laser structures which exhibit remarkable properties highlighted by ultra-narrow spectral emission and temperature-insensitive operation. An emerging application of such QDs is manipulation of optically induced coherent states of the QDs using ultra-short pulses. The most important of those is a demonstration of the hallmark quantum optics phenomena: collapse and revival of wave functions induced and observed in a QD ensemble in the form of an optical amplifier. The observation of quantum coherent revivals was not observed previously in solids, and in all media it was demonstrated only at cryogenic temperatures. Furthermore, coherently excited discrete homogeneous QD subgroups within an ensemble act as multiple quantum bits, resembling molecules in nuclear magnetic resonance (NMR) and can equally serve for quantum communication, simulation and sensing applications. The room temperature QDs exhibit a record long dephasing time (T2), we envision therefore a host of future compact quantum devices based on high quality QDs which do not require cryogenic cooling.