Abstract
The development of scalable sources of non-classical light is fundamental to unlocking the technological potential of quantum photonics. Semiconductor quantum dots are emerging as near-optimal sources of indistinguishable single photons. However, their performance as sources of entangled-photon pairs are still modest compared to parametric down converters. Photons emitted from conventional Stranski–Krastanov InGaAs quantum dots have shown non-optimal levels of entanglement and indistinguishability. For quantum networks, both criteria must be met simultaneously. Here, we show that this is possible with a system that has received limited attention so far: GaAs quantum dots. They can emit triggered polarization-entangled photons with high purity (g(2)(0) = 0.002±0.002), high indistinguishability (0.93±0.07 for 2 ns pulse separation) and high entanglement fidelity (0.94±0.01). Our results show that GaAs might be the material of choice for quantum-dot entanglement sources in future quantum technologies.
Highlights
The development of scalable sources of non-classical light is fundamental to unlocking the technological potential of quantum photonics
We begin with the characterization of our (GaAs)/AlGaAs quantum dots (QDs), which were obtained by infilling nanoholes created by in situ droplet etching of AlGaAs layers[25,26]
This observation is qualitatively ascribed to the large number of confined states in the employed QDs, which lead to many possible charge configurations competing with the XX at high excitation power
Summary
The development of scalable sources of non-classical light is fundamental to unlocking the technological potential of quantum photonics. The ideal source of quantum light, for example, should deliver single and entangled photons deterministically, with high purity, high efficiency, high indistinguishability and high degree of entanglement, and it should be compatible with current photonic integration technologies Implementing such a source, is far from an easy task[2,3]. If we restrict the discussion to single photon sources[4], that is if we disregard entanglement, semiconductor quantum dots (QDs) have recently demonstrated their capability to fulfill all the requirements on the wish list, carrying great promise for the implementation of photonic quantum networks[1] This is eventually testified by the increasing interest of the community working with parametric down converters[5,6,7], the workhorse sources of non-classical light that have been used to achieve a wealth of breakthroughs in quantum optics. This approach is not straightforward to implement experimentally, as the effect of a magnetic field on the X states depends strongly on its direction and can give rise to off-diagonal terms in the X Hamiltonian that cannot be compensated with external fixes
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