Quantum-light sources based on semiconductor quantum dots (QDs) are promising candidates for many applications in quantum photonics and quantum communication. Important emission characteristics of such emitters, namely the single-photon purity and photon indistinguishability, are usually assessed via time-correlated measurements using standard 'click' detectors in Hanbury Brown and Twiss or Hong-Ou-Mandel (HOM-) type configurations. In this work, we employ a state-of-theart photon-number-resolving (PNR) detection system based on superconducting transition-edge sensors (TESs) to directly access the photon-number distribution of deterministically fabricated solidstate single-photon sources. Offering quantum efficiencies close to unity and high energy resolution, our TES-based two-channel detector system allows us to analyse the quantum optical properties of a QD-based non-classical light source. In particular, it enables the direct observation of the two-particle Fock-state resulting from interference of quantum mechanically indistinguishable photons in HOMexperiments. Additionally, comparative measurements reveal excellent quantitative agreement of the photon-indistinguishabilities obtained with PNR ((90±7)%) and standard click ((90±5)%) detectors. Our work thus demonstrates that TES-based detectors are perfectly suitable for the quantum metrology of non-classical light sources and higlights appealing prospects for the efficient implementation of quantum information tasks based on multi-photon states.
Experiments described in the literature lead to different formulae for saturation corrections in ionization chambers. To elucidate the differences, saturation curves of an extrapolation chamber irradiated with beta particles from 90Sr+90Y sources have been studied experimentally. The results could be described by one formula which was a combination of known formulae for charge collection losses due to volume recombination, initial recombination and diffusion.
We report on two-photon interference (TPI) experiments using remote deterministic single-photon sources. Employing 3D in-situ electron-beam lithography, we fabricate quantum-light sources at specific target wavelengths by integrating pre-selected semiconductor quantum dots within monolithic microlenses. The individual single-photon sources show TPI visibilities of 49% and 22%, respectively, under pulsed p-shell excitation at 80 MHz. For the mutual TPI of the remote sources, we observe an uncorrected visibility of 29%, in quantitative agreement with the pure dephasing of the individual sources. Due to its efficient photon extraction within a broad spectral range (> 20 nm), our microlens-based approach is predestinated for future entanglement swapping experiments utilizing entangled photon pairs emitted by distant biexciton-exciton radiative cascades.
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Additive manufacturing by electron beam melting (EBM) is a complex process, which still lacks reliable tools for process monitoring. Demanding processing conditions such as high temperature, high vacuum, and X‐ray radiation impede the continuous operation of standard process monitoring devices such as light‐optical camera systems. To overcome this deficit, the detection of backscattered electrons (BSEs) is a highly promising approach. A detection system for BSEs is used for recording the in operando signal during melting inside an EBM system. The acquired data are postprocessed by mapping the data points to spatial coordinates. A comparison between the obtained intensity map and the as‐built surface shows a remarkable correlation, which might be suitable for process monitoring and quality control purposes.
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