Departmental Seminar

Accelerating optical quantum technologies with quantum-dot based devices

Dr Niccolo Somaschi
Quandela, France

In the growing development of quantum technologies, optical based systems are yet to achieve such levels of efficiency and fidelity to allow for the realization of complex structures dedicated to quantum simulations, as in the case of superconducting circuits, trapped ions and cold atoms. Nevertheless, flying qubits (light) represent the preferable mean to interconnect quantum nodes and develop secure quantum networks on the large scale, as recently achieved in large cities and even between earth  and a low-orbit satellite.

The strong limiting factors which are holding back a large-scale implementation of optical quantum technologies are related to the low efficiency of heralded single-photon sources and by the probabilistic operation of two-photon gates. Deterministic operation of these two elements can in principle be obtained by making use of single-photon sensitivity proper of atomic transitions. In this context, artificial atoms in the form of semiconductor quantum dots, have emerged as a promising system to scale up optical quantum technologies, offering the potential of integration and scalability.

In this talk I will review some recent progresses along this research line. I will discuss how a single quantum dot can be positioned in an optical cavity in a fully controlled way so as to obtain single-photon sources with single-photon purity and indistinguishability over 99% and brightness exceeding by a factor 20 the one of currently used sources based on parametric down conversion, allowing for a considerable speed-up of quantum protocols, such as boson sampling.

I will also present our latest progresses towards the development of deterministic two-photon gates with devices performing as nonlinear switches at the single-photon level, converting a coherent pulse into a highly non-classical light wave-packet.

In the last part of the talk I will introduce a newly created spin-off company, QUANDELA, which aim is to commercialize solid-state based single-photon sources for the advancement of optical quantum technologies for quantum computation and simulation, quantum communication, imaging and metrology.

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