Efficient Sources of Entangled Photon Pairs Based on Deterministic Quantum Dot Microlenses
Final Report Abstract
The bilateral project, with partners at the Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, and the Technische Universität Berlin, developed bright sources of polarization-entangled photon pairs based on InGaAs quantum dots (QDs) grown on (111) oriented GaAs substrates. The (111) QDs were grown by droplet epitaxy and were integrated deterministically into microlenses by means of in-situ electron beam lithography (EBL). Optical and quantum optical studies revealed the excellent optical and quantum optical properties of these advanced quantum devices. QD quantum light sources are key elements of advanced quantum communication schemes, such as the quantum repeater, which are based on entanglement distribution. In our concept, single (111) QDs in the active region of the sources enable the generation of polarization-entangled photon-pairs via the biexciton (XX) - exciton (X) radiative cascade due to the unique electronic structure of these QDs with theoretically diminishing fine-structure splitting (FSS). After numerical optimization for maximum photon extraction efficiency, high-quality QD-heterostructures with distributed Bragg reflectors (DBR) were grown by the Russian partner on 2°-misoriented n+ GaAs (111)B substrate. Subsequently, the German partner deterministically integrated suitable (111) QDs into microlenses to ensure broadband enhancement of XX and X emission. The quantum devices were optimized in close interaction between the Russian and German partners in several design, growth, and nano-fabrication iterations to obtain the best possible performance of the final device generation. The emission properties of the (111) QD quantum devices were investigated by extensive optical and quantum optical studies under non-resonant and, for the first time, also strict resonant excitation. These studies revealed the high optical quality of the developed (111) QD with very distinct XX and X emission lines and linewidths down to 12 µeV in resonance fluorescence. In contrast to theoretical predictions, the FSS of as grown (111) QDs could not be reduced to a level of the homogenous linewidth which is attributed to remaining structural imperfections. Applying rapid thermal annealing we could partially overcome this issue and reach FSS values as low as (2.9 ± 0.2) µeV by thermal treatment. With respect to quantum optical properties, the emission of polarization entangled photon pairs was first studied on (100) QDs which provided important insight into the underlying physics and revealed for instance the impact of spin precession on the entanglement fidelity. Quantum tomography measurements on (111) QD-microlenses yielded post selected entanglement fidelity 69.5 % which is highly promising for further optimizations of (111) QD quantum devices. Further studies on the quantum nature of emission via photon autocorrelation measurements and Hong-Ou-Mandel (HOM) experiments revealed excellent multiphoton suppression with g(2)(0) = (7.3 ± 0.5) % and significant HOM visibility of 41 ± 10 % in resonance fluorescence. While being not yet at the level of mature (100) QDs these results indicated once again the high potential of (111) QDs to act as highly attractive quantum emitters in photonic quantum devices. Overall, the project has led to many important results in the field of photonic quantum devices for applications in future quantum networks. The achieved results can pave the way for ultra-bright entangled photon pair sources quantum light sources enabling for instance the implementation of quantum repeater networks. In this regard it will be highly interesting to develop the droplet epitaxy of (111) QDs towards telecom wavelength of 1.3 µm and 1.55 µm for application in fiber-based quantum communication networks.
Publications
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Subminiature emitters based on a single (111) In(Ga)As quantum dot and hybrid microcavity, Semiconductors volume 51, pages 1399–1402 (2017)
I. A. Derebezov, V. A. Gaisler, A. V. Gaisler, D. V. Dmitriev, A. I. Toropov, S. Fischbach, A. Schlehahn, A. Kaganskiy, T. Heindel, S. Bounouar, S. Rodt, S. Reitzenstein
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Generation of maximally entangled states and coherent control in quantum dot microlenses, Appl. Phys. Lett. 112, 153107 (2018)
S. Bounouar, C. de la Haye, M. Strauß, P. Schnauber, A. Thoma, M. Gschrey, J.-H. Schulze, A. Strittmatter, S. Rodt, and S. Reitzenstein
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Spectroscopy of Single AlInAs and (111)-Oriented InGaAs Quantum Dots, Semiconductors 52, 1437–1441 (2018)
I. A. Derebezov, V. A. Gaisler, A. V. Gaisler, D. V. Dmitriev, A. I. Toropov, M. von Helversen, C. de la Haye, S. Bounouar, and S. Reitzenstein
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Non-Markovian features in semiconductor quantum optics: quantifying the role of phonons in experiment and theory, Nanophotonics 8, 655-683 (2019)
A. Carmele and S. Reitzenstein, Stephan
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Nonclassical Light Sources Based on Selectively Positioned Deterministic Microlens Structures and (111) In(Ga)As Quantum Dots. Semiconductors 53, 1304–1307 (2019)
I. A. Derebezov, V. A. Gaisler, A. V. Gaisler, D. V. Dmitriev, A. I. Toropov, M. von Helversen, C. de la Haye, S. Bounouar, and S. Reitzenstein
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Suppressed antibunching via spectral filtering: An analytical study in the two-photon Mollow regime, Phys. Rev. A 99, 023813 (2019)
J. Schleibner, S. Bounouar, M. Strauß, S. Reitzenstein, A. Knorr, and A. Carmele
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Entanglement robustness to excitonic spin precession in a quantum dot, Phys. Rev. B 102, 045304 (2020)
S. Bounouar, G. Rein, K. Barkemeyer, J. Schleibner, P. Schnauber, M. Gschrey, J.-H. Schulze, A. Strittmatter, S. Rodt, A. Knorr, A. Carmele, and S. Reitzenstein
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Quantum light sources based on deterministic microlenses structures with (111) In(Ga)As and AlInAs QDs, J. Phys.: Conf. Ser. 1461, 012028 (2020)
I. A. Derebezov, V. A. Haisler, A. V. Haisler, D. V. Dmitriev, A. I. Toropov, S. Rodt, M. von Helversen, C. de la Haye, S. Bounouar, and S. Reitzenstein
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High-performance deterministic in situ electron-beam lithography enabled by cathodoluminescence spectroscopy, Nano Ex. 2, 014007 (2021)
S. Rodt and S. Reitzenstein
