To make photonic quantum information a reality 1,2 , a number of extraordinary challenges need to be overcome. One of the outstanding challenges is the achievement of large arrays of reproducible "entangled" photon generators, maintaining the compatibility with integration with optical devices and detectors 3,4,5 . Semiconductor quantum dots (QDs) are potentially ideal for this. They allow generating photons on demand 6,7 without relying on probabilistic processes 8,9 . Nevertheless, most QD systems are limited by the intrinsic lack of symmetry, which allows to obtain only a small number (typically 1/100 or worse) of good dots per chip. The recent retraction of Mohan et al. 10 seemed to question the very possibility of matching site-control and high symmetry. Here we show that with a new family of (111) grown pyramidal sitecontrolled InGaAs 1- N  QDs, it is possible to overcome previous difficulties and obtain areas containing as much as 15% of polarization-entangled photon emitters, showing fidelities as high as 0.721±0.043.The idea underlining the principle of entangled photon emission with QDs relies on fundamental quantum physics: particle indistinguishability generates a superposition state when two energetically nearly degenerate quantum levels are populated at the same time. In QDs, entanglement resides in polarization of two photons emitted during the cascaded biexciton-exciton recombination 11 . Here one difficulty arises: when the two excitonic levels are not perfectly degenerate (i.e. there is a fine structure splitting, FSS), the entanglement in the emission persists, but a phase term between the two (linearly) polarized photons proportional to both energy and time is introduced. This results in a relative rotation of the two photon polarizations (not constant in time) making entanglement substantially impossible to be detected in a simple way 12 .All currently reported QD systems allowing entangled photon emission tend to present a large FSS, fundamentally allowing only a few (post-growth selected) QDs on a semiconductor wafer as good sources, while till now no entangled photon emission has been

Nanocrystal/fullerene derivative inorganic-organic hybrid photodetectors exhibiting high detectivity for near-IR wavelengths and a linear power dependence are produced. The ultrafast electron transfer from the PbS crystals to the fullerene opens a new route to obtaining efficient photodetectors that are appealing, cost-effective alternatives to the currently available technology

Exciton-exciton interaction in dot/rod CdSe/CdS nanocrystals has proved to be very sensitive to the shape of nanocrystals, due to the unique band alignment between CdSe and CdS. Repulsive exciton-exciton interaction is demonstrated, which makes CdSe/CdS dot/rods promising gain media for solution-processable lasers, with projected pump threshold densities below 1 kW cm(-2) for continuous wave lasing.

Silicon photonics (SiPh) enables compact photonic integrated circuits (PICs), showing superior performance for a wide variety of applications. Various optical functions have been demonstrated on this platform that allows for complex and powerful PICs. Nevertheless, laser source integration technologies are not yet as mature, hampering the further cost reduction of the eventual Si photonic systems-on-chip and impeding the expansion of this platform to a broader range of applications. Here, we discuss a promising technology, micro-transfer-printing (μTP), for the realization of III-V-on-Si PICs. By employing a polydimethylsiloxane elastomeric stamp, the integration of III-V devices can be realized in a massively parallel manner on a wafer without substantial modifications to the SiPh process flow, leading to a significant cost reduction of the resulting III-V-on-Si PICs. This paper summarizes some of the recent developments in the use of μTP technology for realizing the integration of III-V photodiodes and lasers on Si PICs.