"A quantum dot (QD) in a microcavity is an ideal single spin-single photon interface: the spin of a carrier trapped inside a QD can be used as a quantum bit and the coupling to photons can allow remote spin entanglement. A QD in a cavity can also generate single photons or entangled photon pairs, often referred to as flying quantum bit. Controlling the QD spontaneous emission is crucial to ensure optimal coupling of the photon and spin states. The present project relies on a unique and original technology we have developed which allows us to deterministically control the QD-cavity system. With this technique, we can fabricate a large number of identical coupled QD-cavity devices operating either in the weak or strong coupling regime. The potential of the technique has been proven by the fabrication of the brightest source of entangled photon pairs to date (Nature 2010).
The objective of the present project is to build up a platform for basic quantum operations using QDs in cavities. The first aim is to develop highly efficient light emitting devices emitting indistinguishable single photons and entangled photon pairs. The mechanisms leading to quantum decoherence in QD based sources will be investigated. We will also explore a new generation of devices where QDs are coupled to plasmonic nano-antenna. The second objective is to implement basic quantum operations ranging from entanglement purification to quantum teleportation using QD based sources. The third objective of the project is to control the spin-photon interface. We first aim at demonstrating quantum non-demolition spin measurement through highly sensitive off-resonant Faraday rotation. We then aim at entangling two spins separated by macroscopic distances, using their controlled interaction with photons. This will be obtained either by making a single photon interact with two spin in cavities or by interfering indistinguishable photons emitted by two independent charged QDs."
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