| 1. |
- Brodu, Annalisa, et al.
(författare)
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Exciton Fine Structure and Lattice Dynamics in InP/ZnSe Core/Shell Quantum Dots
- 2018
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:8, s. 3353-3362
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline InP quantum dots (QDs) hold promise for heavy-metal-free optoelectronic applications due to their bright and size tunable emission in the visible range. Photochemical stability and high photoluminescence (PL) quantum yield are obtained by a diversity of epitaxial shells around the InP core. To understand and optimize the emission line shapes, the exciton fine structure of InP core/shell QD systems needs be investigated. Here, we study the exciton fine structure of InP/ZnSe core/shell QDs with core diameters ranging from 2.9 to 3.6 nm (PL peak from 2.3 to 1.95 eV at 4 K). PL decay measurements as a function of temperature in the 10 mK to 300 K range show that the lowest exciton fine structure state is a dark state, from which radiative recombination is assisted by coupling to confined acoustic phonons with energies ranging from 4 to 7 meV, depending on the core diameter. Circularly polarized fluorescence line-narrowing (FLN) spectroscopy at 4 K under high magnetic fields (up to 30 T) demonstrates that radiative recombination from the dark F = +/- 2 state involves acoustic and optical phonons, from both the InP core and the ZnSe shell. Our data indicate that the highest intensity FLN peak is an acoustic phonon replica rather than a zero-phonon line, implying that the energy separation observed between the F = +/- 1 state and the highest intensity peak in the FLN spectra (6 to 16 meV, depending on the InP core size) is larger than the splitting between the dark and bright fine structure exciton states.
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| 2. |
- Fognini, A., et al.
(författare)
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Universal fine-structure eraser for quantum dots
- 2018
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 26:19, s. 24487-24496
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the degree of entanglement measurable from a quantum dot via the biexciton-exciton cascade as a function of the exciton fine-structure splitting and the detection time resolution. We show that the time-energy uncertainty relation provides means to measure a high entanglement even in presence of a finite fine-structure splitting when a detection system with high temporal resolution is employed. Still, in many applications it would be beneficial if the fine-structure splitting could be compensated to zero. To solve this problem, we propose an all-optical approach with rotating waveplates to erase this fine-structure splitting completely which should allow obtaining a high degree of entanglement with near-unity efficiency. Our optical approach is possible with current technology and is also compatible with any quantum dot showing fine-structure splitting. This bears the advantage that for example the fine-structure splitting of quantum dots in nanowires and micropillars can be directly compensated without the need for further sample processing.
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| 3. |
- Gao, Jun, et al.
(författare)
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Coexistence of extended and localized states in finite-sized mosaic Wannier-Stark lattices
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 108:14
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Tidskriftsartikel (refereegranskat)abstract
- Quantum transport and localization are fundamental concepts in condensed matter physics. It is commonly believed that in one-dimensional systems, the existence of mobility edges is highly dependent on disorder. Recently, there has been a debate over the existence of an exact mobility edge in a modulated mosaic model without quenched disorder, the so-called mosaic Wannier-Stark lattice. Here, we experimentally implement such disorder-free mosaic photonic lattices using a silicon photonics platform. By creating a synthetic electric field, we could observe energy-dependent coexistence of both extended and localized states in a finite number of waveguides. The Wannier-Stark ladder emerges when the resulting potential is strong enough, and can be directly probed by exciting different spatial modes of the lattice. Our studies provide the experimental proof of coexisting sets of strongly localized and conducting (though weakly localized) states in finite-sized mosaic Wannier-Stark lattices, which hold the potential to encode high-dimensional quantum resources with compact and robust structures.
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| 4. |
- Lagoudakis, K. G., et al.
(författare)
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Ultrafast coherent manipulation of trions in site-controlled nanowire quantum dots
- 2016
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 3:12, s. 1430-1435
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Tidskriftsartikel (refereegranskat)abstract
- Physical implementations of large-scale quantum processors based on solid-state platforms benefit from realizations of quantum bits positioned in regular arrays. Self-assembled quantum dots are well established as promising candidates for quantum optics and quantum information processing, but they are randomly positioned. Site-controlled quantum dots, on the other hand, are grown in pre-defined locations but have not yet been sufficiently developed to be used as a platform for quantum information processing. In this paper, we demonstrate all-optical ultrafast complete coherent control of a qubit formed by the single-spin/trion states of a charged site-controlled nanowire quantum dot. Our results show that site-controlled quantum dots in nanowires are promising hosts of charged-exciton qubits and that these qubits can be cleanly manipulated in the same fashion as has been demonstrated in randomly positioned quantum dot samples. Our findings suggest that many of the related excitonic qubit experiments that have been performed over the past 15 years may work well in the more scalable, site-controlled systems, making them very promising for the realization of quantum hardware.
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| 5. |
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| 6. |
- Zadeh, I. E., et al.
(författare)
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Scalable quantum optics with nanowires
- 2019
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580569
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Konferensbidrag (refereegranskat)abstract
- Single-photon generation, processing, and detection are the three main components of any quantum optical circuit. We present our results on integration of semiconducting nanowire quantum dots, dielectric waveguides, and ultrahigh performance superconducting nanowire single-photon detectors.
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| 7. |
- Zwiller, V., et al.
(författare)
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Fabrication and time-resolved studies of visible microdisk lasers
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:4, s. 2307-2309
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Tidskriftsartikel (refereegranskat)abstract
- We report on the fabrication and characterization of microdisk lasers emitting at around 650 nm. The structures were grown by metalorganic vapor phase epitaxy and processed using electron beam lithography and wet etching. Time-resolved photoluminescence measurements done at low temperature show a lasing threshold of 60 muW average power. A redshift in the whispering modes energy is observed.
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| 8. |
- Zwiller, V, et al.
(författare)
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Generating visible single photons on demand with single InP quantum dots
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:10, s. 1509-1511
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Tidskriftsartikel (refereegranskat)abstract
- We present photon correlation measurements performed on a device based on single InP quantum dots. The device consists of a 400 nm thick membrane containing a low density of quantum dots on a metal mirror. Measurements done under continuous excitation reveal a very pronounced antibunching dip while measurements done under pulsed excitation enable the generation of single photons on demand at the optimum wavelength for silicon-based single-photon detectors.
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| 9. |
- Zwiller, Val, et al.
(författare)
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Single-photon detection with near unity efficiency, ultrahigh detection-rates, and ultra-high time resolution
- 2017
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Ingår i: CLEO: Science and Innovations part of CLEO: 2017 : 4-19 May 2017, San Jose, California, United States. - : Optical Society of America. - 9781943580279
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Konferensbidrag (refereegranskat)abstract
- Single-photon detectors with high efficiency, high time resolution, low dark counts and high photon detection-rates are vital for most demanding quantum optics experiments. Combining all performances in a single device has been challenging. Here, we demonstrate a broadband detector with efficiency higher than 92%, over 150 MHz photon detection-rate and dark counts below 130 Hz operated in a conventional Gifford-McMahon cryostat. Furthermore, using our custom made cryogenic amplifiers and optimized detector, we reach a record low jitter of 14.80 ps while maintaining high efficiency.
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| 10. |
- Zwiller, V., et al.
(författare)
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Studies of self-assembled InP quantum dots in planar microcavities
- 2000
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Ingår i: Materials Science and Engineering B: Solid-State Materials for Advanced Technology. - Strasbourg, France. ; 69:Lausanne, Switzerland, s. 314-317
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled InP quantum dots have been grown in planar microcavities. The dots were embedded in a Ga0.52In0.48P spacer grown on top of a high reflectance epitaxial Al0.29Ga0.71As/AlAs distributed Bragg reflector (DBR) to obtain a 33λ/4 cavity. The Fabry-Perot microcavity is formed between the AlGaAs/AlAs DBR and a dielectric SiNx/SiO2 DBR deposited on top of the GaInP spacer. The quantum dot emission is centered at 1.62 eV at 7 K. The microcavity resonance is centered at 1.65 eV, with a linewidth of 2 meV. Micro-photoluminescence (PL) studies using different objectives with different numerical apertures enable the collection of transversal modes.
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