A semiconductor quantum dot is a promising system to develop a solid-state quantum network. Like real atoms, quantum dots can emit single photons, polarization entangled photon pairs, indistinguishable photons… Moreover, the spin of a carrier trapped in a quantum dot can present long coherence times and be used as a stationary quantum bit that one can optically manipulate and measure. However, the scalability of a quantum dot based quantum network requires implementing a highly efficient single photon-single quantum dot interface so as to collect every photon emitted by a quantum dot and symmetrically, to ensure that every photon sent onto the device interacts with the quantum dot. Controlling the spontaneous emission of a quantum dot in a cavity is an efficient way to build such an interface. In this talk, we will present our recent results along this research line.
We have developed an in-situ lithography technique to deterministically insert a single quantum dot into a pillar optical microcavity. In the light-matter weak coupling regime, we obtain ultrabright sources of quantum light. We demonstrate sources of indistinguishable single photons with brightness as large as 79 % collected photon per pulse. With coupled pillar cavities, we also fabricate bright sources of polarization entangled photon pairs. The potential of these sources for quantum information processing is demonstrated by implementing an entangling controlled-NOT gate. In the light matter strong coupling regime, we demonstrate optical non-linearities for only 8 incident photons per pulse. Finally, we present a novel photonic structure and a technology allowing the electrical control of the devices, a critical step for the scalability of a quantum network based on semiconductor quantum dots.
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