1,351 research outputs found
High-yield fabrication of entangled photon emitters for hybrid quantum networking using high-temperature droplet epitaxy
Several semiconductor quantum dot techniques have been investigated for the
generation of entangled photon pairs. Among the other techniques, droplet
epitaxy enables the control of the shape, size, density, and emission
wavelength of the quantum emitters. However, the fraction of the
entanglement-ready quantum dots that can be fabricated with this method is
still limited to around 5%, and matching the energy of the entangled photons to
atomic transitions (a promising route towards quantum networking) remains an
outstanding challenge.
Here, we overcome these obstacles by introducing a modified approach to
droplet epitaxy on a high symmetry (111)A substrate, where the fundamental
crystallization step is performed at a significantly higher temperature as
compared to previous reports. Our method drastically improves the yield of
entanglement-ready photon sources near the emission wavelength of interest,
which can be as high as 95% due to the low values of fine structure splitting
and radiative lifetime, together with the reduced exciton dephasing offered by
the choice of GaAs/AlGaAs materials. The quantum dots are designed to emit in
the operating spectral region of Rb-based slow-light media, providing a viable
technology for quantum repeater stations.Comment: 14 pages, 3 figure
Generation of maximally entangled states and coherent control in quantum dot microlenses
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 112, 153107 (2018) and may be found at https://doi.org/10.1063/1.5020242.The integration of entangled photon emitters in nanophotonic structures designed for the broadband enhancement of photon extraction is a major challenge for quantum information technologies. We study the potential of quantum dot (QD) microlenses as efficient emitters of maximally entangled photons. For this purpose, we perform quantum tomography measurements on InGaAs QDs integrated deterministically into microlenses. Even though the studied QDs show non-zero excitonic fine-structure splitting (FSS), polarization entanglement can be prepared with a fidelity close to unity. The quality of the measured entanglement is only dependent on the temporal resolution of the applied single-photon detectors compared to the period of the excitonic phase precession imposed by the FSS. Interestingly, entanglement is kept along the full excitonic wave-packet and is not affected by decoherence. Furthermore, coherent control of the upper biexcitonic state is demonstrated.DFG, SFB 787, Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeBMBF, 03V0630TIB, Entwicklung einer Halbleiterbasierten Einzelphotonenquelle fĂĽr die Quanteninformationstechnologi
High coherence photon pair source for quantum communication
This paper reports a novel single mode source of narrow-band entangled photon
pairs at telecom wavelengths under continuous wave excitation, based on
parametric down conversion. For only 7 mW of pump power it has a created
spectral radiance of 0.08 pairs per coherence length and a bandwidth of 10 pm
(1.2 GHz). The effectively emitted spectral brightness reaches 3.9*10^5 pairs
/(s pm). Furthermore, when combined with low jitter single photon detectors,
such sources allow for the implementation of quantum communication protocols
without any active synchronization or path length stabilization. A HOM-Dip with
photons from two autonomous CW sources has been realized demonstrating the
setup's stability and performance.Comment: 12 pages, 4 figure
Strain-Tunable GaAs Quantum dot: A Nearly Dephasing-Free Source of Entangled Photon Pairs on Demand
Entangled photon generation from semiconductor quantum dots via the
biexciton-exciton cascade underlies various decoherence mechanisms related to
the solid-state nature of the quantum emitters. So far, this has prevented the
demonstration of nearly-maximally entangled photons without the aid of
inefficient and complex post-selection techniques that are hardly suitable for
quantum communication technologies. Here, we tackle this challenge using
strain-tunable GaAs quantum dots driven under two-photon resonant excitation
and with strictly-degenerate exciton states. We demonstrate experimentally that
our on-demand source generates polarization-entangled photons with fidelity of
0.978(5) and concurrence of 0.97(1) without resorting to post-selection
techniques. Moreover, we show that the remaining decoherence mechanisms can be
overcome using a modest Purcell enhancement so as to achieve a degree of
entanglement >0.99. Our results highlight that GaAs quantum dots can be readily
used in advanced communication protocols relying on the non-local properties of
quantum entanglement
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