Among different quantum information processing (QIP) architectures, photons traveling either in free space or in integrated-waveguide circuits are very appealing due to their propagation speed and negligible decoherence. One of the longstanding roadblocks towards practical applications of photonic-based QIP has been the lack of deterministic photon sources. Semiconductor quantum dots (QDs) can generate both single and entangled photon pairs with high quality and high rates. As such, they may provide the ultimate solution to the “source bottleneck”.

The main aim of this project is to establish a world-leading single- and entangled-photon source platform based on an emerging class of QDs and use it to demonstrate multiphoton quantum protocols in free-space and waveguide circuits. To reach this goal, we will combine complementary expertise in QD physics and devices and theoretical and experimental QIP.

We will focus our efforts on QDs made of Gallium Arsenide (GaAs) inclusions in an Aluminum Gallium Arsenide (AlGaAs) matrix. Such QDs have recently shown a unique combination of appealing features: fast radiative rates of ~5 GHz, capability of generating near perfectly entangled photon pairs with excellent indistinguishability and ultralow multiphoton emission probability, as well as wavelength matched to the high-sensitivity range of silicon-based single-photon detectors. Substantial efforts are however necessary to increase the brightness and indistinguishability of the photons emitted by single and multiple sources. We will tackle these challenges by (i) integrating optimized QD sources in photonic structures designed to feature broadband photon-extraction-efficiency and Purcell enhancement (ii) exploring different coherent and incoherent excitation schemes suitable for the chosen QDs. In parallel to the progress in source performance, we will design few-qubits applications with increasing complexity and implement them in high-performance photonic chips. These will include boson sampling, fusion gates, and cluster-states generation for secure quantum computing. New entanglement witnesses will be constructed to verify the generation of multipartite entanglement in the experiment and assess the role of residual imperfections.   

In the long term, we expect that this project will allow us to explore the ultimate limits of photonic QIP.