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Register a new userIndistinguishable single photons from spatially-ordered array of highly efficient and pure mesa-top single quantum dots: A step closer to on-chip quantum optical circuits
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Added by
Swarnabha Chattaraj
Publication date
2021
fields
Physics
and research's language is
English
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The first two decades of the 21st century have witnessed remarkable progress in harnessing the power of quantum mechanics, on-chip, enabled by the development in epitaxial semiconductor nanoscience with proof-of-principle demonstrations -- many tour-de force -- of quantum functionalities such as entanglement and teleportation amongst photon and matter qubits ---quintessential quantum phenomena that underpin the development of quantum technologies. A basic hindrance to such development however has been the absence of a platform of on-demand single photon sources (SPSs) with adequate spectral characteristics and arranged in spatially regular arrays necessary for their incorporation in surrounding light manipulation units to enable quantum networks. Here we report on the first spatially-ordered, scalable platform of deterministic, bright, spectrally highly uniform, pure, and indistinguishable SPSs. At 19.5K, and without Purcell enhancement, these SPSs exhibit emission purity ~99.2% and two-photon interference (TPI) indistinguishability ~57%. Oscillation behavior of the photon emission indicates that the photons originate from a coherent superposition of two excitonic states, revealing effectively a three-level electronic structure which can be exploited as potential two-frequency qubit generating energy entangled photons for teleportation. Time-dependent two photon interference (Hong-Ou Mandel interferometry) coincidence counts g(2)({tau}) near {tau}=0 show effectively zero count which, analyzed using the three-level model, reveals a highly encouraging dephasing time of ~0.58ns at ~20K. Such SPS arrays in a planarized structure open the pathway to creating interconnected quantum networks for application in communication, sensing, computing and more.
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Semiconductor quantum dots are converging towards the demanding requirements of photonic quantum technologies. Among different systems, quantum dots with dimensions exceeding the free-exciton Bohr radius are appealing because of their high oscillator strengths. While this property has received much attention in the context of cavity quantum electrodynamics, little is known about the degree of indistinguishability of single photons consecutively emitted by such dots and on the proper excitation schemes to achieve high indistinguishability. A prominent example is represented by GaAs quantum dots obtained by local droplet etching, which recently outperformed other systems as triggered sources of entangled photon pairs. On these dots, we compare different single-photon excitation mechanisms, and we find (i) a phonon bottleneck and poor indistinguishability for conventional excitation via excited states and (ii) photon indistinguishablilities above 90% for both strictly resonant and for incoherent acoustic- and optical-phonon-assisted excitation. Among the excitation schemes, optical phonon-assisted excitation enables straightforward laser rejection without a compromise on the source brightness together with a high photon indistinguishability.
Single photons coupled to atomic systems have shown to be a promising platform for developing quantum technologies. Yet a bright on-demand, highly pure and highly indistinguishable single-photon source compatible with atomic platforms is lacking. In this work, we demonstrate such a source based on a strongly interacting Rydberg system. The large optical nonlinearities in a blockaded Rydberg ensemble convert coherent light into a single-collective excitation that can be coherently retrieved as a quantum field. We observe a single-transverse-mode efficiency up to 0.18(2), $g^{(2)}=2.0(1.5)times10^{-4}$, and indistinguishability of 0.982(7), making this system promising for scalable quantum information applications. Accounting for losses, we infer a generation probability up to 0.40(4). Furthermore, we investigate the effects of contaminant Rydberg excitations on the source efficiency. Finally, we introduce metrics to benchmark the performance of on-demand single-photon sources.
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