A5080627879- Semiconductor Quantum Structures and Devices
- Quantum Information and Cryptography
- Semiconductor Lasers and Optical Devices
- Neural Networks and Reservoir Computing
- Photonic and Optical Devices
- Quantum and electron transport phenomena
- Quantum optics and atomic interactions
- Quantum Mechanics and Applications
- Quantum Computing Algorithms and Architecture
- Quantum Dots Synthesis And Properties
- Acoustic Wave Resonator Technologies
- Optical Network Technologies
- Mechanical and Optical Resonators
- Advanced Sensor and Energy Harvesting Materials
- Nanowire Synthesis and Applications
- Advanced Optical Sensing Technologies
- Quantum-Dot Cellular Automata
- Molecular Communication and Nanonetworks
- GaN-based semiconductor devices and materials
- Strong Light-Matter Interactions
- Silicon Nanostructures and Photoluminescence
- Plasmonic and Surface Plasmon Research
- Nonlinear Optical Materials Studies
- Spectroscopy and Quantum Chemical Studies
- Advanced Optical Network Technologies
Johannes Kepler University of Linz
2016-2024
Entangled photon generation from semiconductor quantum dots via the biexciton-exciton cascade underlies various decoherence mechanisms related to solid-state nature of emitters. So far, this has prevented demonstration nearly-maximally entangled photons without aid inefficient and complex post-selection techniques that are hardly suitable for communication technologies. Here, we tackle challenge using strain-tunable GaAs driven under two-photon resonant excitation with strictly-degenerate...
State-of-the-art quantum key distribution systems are based on the BB84 protocol and single photons generated by lasers. These implementations suffer from range limitations security loopholes, which require expensive adaptation. The use of polarization entangled photon pairs substantially alleviates threads while allowing for basically arbitrary transmission distances when embedded in repeater schemes. Semiconductor dots capable emitting highly with ultra-low multi-pair emission probability...
Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test quantum mechanics and an essential resource to realization networks. Probabilistic sources nonclassical light were used for seminal demonstration but applications in technologies demand push-button operation requiring single emitters. This, however, turned out be extraordinary challenge due stringent prerequisites on efficiency purity generation entangled states. Here we...
Abstract The prospect of using the quantum nature light for secure communication keeps spurring search and investigation suitable sources entangled photons. A single semiconductor dot is one most attractive, as it can generate indistinguishable photons deterministically compatible with current photonic-integration technologies. However, lack control over energy hampering exploitation dissimilar dots in protocols requiring teleportation entanglement remote locations. Here we introduce...
Photonic quantum technologies are on the verge of finding applications in everyday life with cryptography and internet horizon. Extensive research has been carried out to determine suitable emitters single epitaxial dots emerging as near-optimal sources bright, on-demand, highly indistinguishable photons entangled photon pairs. In order build up networks, it is now essential interface remote emitters. However, this still an outstanding challenge, states dissimilar 'artificial atoms' have be...
The generation and long-haul transmission of highly entangled photon pairs is a cornerstone emerging photonic quantum technologies with key applications such as distribution distributed computing. However, natural limit for the maximum distance inevitably set by attenuation in medium. A network repeaters containing multiple sources photons would allow overcoming this limit. For purpose, requirements on source's brightness pairs' degree entanglement indistinguishability are stringent. Despite...
The tailoring of the physical properties semiconductor nanomaterials by strain has been gaining increasing attention over last years for a wide range applications such as electronics, optoelectronics and photonics. ability to introduce deliberate fields with controlled magnitude in reversible manner is essential fundamental studies novel materials may lead realization advanced multi-functional devices. A prominent approach consists integration active nanomaterials, thin epitaxial films or...
Photons generated on-demand by artificial atoms are used to demonstrate quantum teleportation.
This Perspective presents an overview on the epitaxial growth and optical properties of GaAs quantum dots obtained with droplet etching method as high-quality sources light. We illustrate recent achievements regarding generation single photons polarization entangled photon pairs use these in applications central importance communication such entanglement swapping key distribution.
Semiconductor 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 context cavity electrodynamics, little is known about degree indistinguishability single photons consecutively emitted by such and on proper excitation schemes to achieve indistinguishability. A prominent example represented GaAs obtained local droplet etching, which recently outperformed other systems...
Entangled photon pairs are key to many novel applications in quantum technologies. Semiconductor dots can be used as sources of on-demand, highly entangled photons. The fidelity a fixed maximally state is limited by the excitonic fine-structure splitting. This work demonstrates that, even if this splitting absent, degree entanglement cannot reach unity when excitation pulse two-photon resonance scheme has finite duration. degradation its origin dynamically induced exciton states caused laser...
High-purity multi-photon states are essential for photonic quantum computing. Among existing platforms, semiconductor dots offer a promising route to scalable and deterministic state generation. However, fully realize their potential we require suitable optical excitation method. Current approaches of generation rely on active polarization-switching elements (e.g., electro-optic modulators, EOMs) spatio-temporally demultiplex single photons. Yet, the achievable rate is fundamentally limited...
The optical selection rules in epitaxial quantum dots are strongly influenced by the orientation of their natural quantization axis, which is usually parallel to growth direction. This configuration well suited for vertically emitting devices, but not planar photonic circuits because poorly controlled transition dipoles plane. Here we show that axis gallium arsenide can be flipped into plane via moderate uniaxial stress. By using piezoelectric strain actuators featuring strain-amplification...
Epitaxial GaAs quantum dots grown by droplet etching have recently shown excellent properties as sources of single photons well entangled photon pairs. Integration in some nanophotonic structures requires surface-to-dot distances less than 100 nm. This demands a surface passivation scheme, which could be useful to lower the density states. To address this issue, sulphur with dielectric overlayer an encapsulation is used for QD ≲40 nm, results partial recovery emission linewidths bulk values...
Entanglement-based quantum key distribution (QKD) promises enhanced robustness against eavesdropping and compatibility with future networks. Among other sources, semiconductor dots (QDs) can generate polarization-entangled photon pairs near-unity entanglement fidelity a multiphoton emission probability close to zero even at maximum brightness. These properties have been demonstrated under resonant two-photon excitation (TPE) operation temperatures below 10 K. However, source blinking is...
Abstract The realization of a functional quantum repeater is one the major research goals in long-distance communication. Among different approaches that are being followed, relying on memories interfaced with deterministic emitters considered as most promising solutions. In this work, we focus hardware to implement memory-based quantum-repeater schemes rely semiconductor dots (QDs) for generation polarization entangled photons. Going through relevant figures merit related efficiency photon...
Entangled photon pairs are essential for a multitude of quantum photonic applications. To date, the best performing solid-state emitters entangled photons semiconductor dots operated around liquid-helium temperatures. favor widespread deployment these sources, it is important to explore and understand their behavior at temperatures accessible with compact Stirling coolers. Here we study polarization entanglement among from biexciton–exciton cascade in GaAs up ∼65 K. We observe degradation...
Strain engineering allows the physical properties of materials and devices to be widely tailored, as paradigmatically demonstrated by strained transistors semiconductor lasers employed in consumer electronics. For this reason, its potential impact on our society has been compared that chemical alloying. Although significant progress made last years nanomaterials, strain fields (which are tensorial nature, with six independent components) still mostly used a "scalar" and/or static fashion....
Semiconductor quantum dots have emerged as an especially promising platform for the generation of polarization-entangled photon pairs. However, it was demonstrated recently that two-photon excitation scheme employed in state-of-the-art experiments limits achievable degree entanglement by introducing which-path information. In this work, combined impact and longitudinal acoustic phonons on pairs emitted strongly-confining is investigated. It found further reduce even limit vanishing...
Solid-state quantum emitters embedded in circular Bragg resonators are attractive due to their ability emit light with high brightness and low multiphoton probability. As for any emitter-microcavity system, fabrication imperfections limit the spatial spectral overlap of emitter cavity mode, thus limiting coupling strength. Here, we show that an initial mismatch can be corrected after device by repeated wet chemical etching steps. We demonstrate ∼16 nm wavelength tuning optical modes AlGaAs...
Light emission from solid-state quantum emitters is inherently prone to environmental decoherence, which results in a line broadening and the deterioration of photon indistinguishability. Here we employ correlation Fourier spectroscopy (PCFS) study temporal evolution such two prominent systems: GaAs In(Ga)As dots. Differently previous experiments, are driven with short laser pulses as required for generation high-purity single photons, time scales probe range few nanoseconds milliseconds...
Abstract Photonic structures capable of enhancing the light‐outcoupling efficiency embedded epitaxial quantum dots (QDs) in a broad spectral range are attractive for realization bright sources single photons and entangled photon pairs. In this work, planar‐multilayer antenna is experimentally demonstrated GaAs QDs AlGaAs membranes. The consists metal (Au or Ag) reflector semi‐transparent (Ag) director, with thin oxide layer (hafnium dioxide (HfO 2 ) aluminium (Al O 3 )) between semiconductor...
The optical properties of excitons confined in initially unstrained GaAs/AlGaAs quantum dots are studied as a function variable quasiuniaxial stress. To allow the validation state-of-the-art computational tools for describing nanostructures, we determine dot morphology and in-plane components externally induced strain tensor at positions. Based on these experimental parameters, calculate strain-dependent excitonic emission energy, degree linear polarization, fine-structure splitting using...