A5048798512- Semiconductor Quantum Structures and Devices
- Quantum and electron transport phenomena
- Strong Light-Matter Interactions
- Photonic and Optical Devices
- Thermal Radiation and Cooling Technologies
- Quantum Information and Cryptography
- Advancements in Semiconductor Devices and Circuit Design
- Photonic Crystals and Applications
- Neural Networks and Reservoir Computing
- Quantum optics and atomic interactions
- Plasmonic and Surface Plasmon Research
- Semiconductor Lasers and Optical Devices
- Magnetic properties of thin films
- Mechanical and Optical Resonators
- Semiconductor materials and devices
- Molecular Junctions and Nanostructures
- Nanowire Synthesis and Applications
- Quantum Electrodynamics and Casimir Effect
- Magneto-Optical Properties and Applications
- Quantum Dots Synthesis And Properties
- 2D Materials and Applications
- Advanced Scientific Techniques and Applications
- Radio Frequency Integrated Circuit Design
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
University of Sheffield
2012-2024
University of Exeter
2024
University of St Andrews
2024
TU Dortmund University
2024
Engineering and Physical Sciences Research Council
2014
Osipyan Institute of Solid State Physics RAS
2004-2007
University of Würzburg
2007
Russian Academy of Sciences
2005
Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic in integrated circuit geometries. Within this context, dots possess well-defined spin states (matter qubits), which couple efficiently to photons. By embedding them nanophotonic waveguides, they provide a promising platform for technology implementations. In paper, we demonstrate that the naturally occurring electromagnetic field chirality arises nanobeam waveguides leads unidirectional...
Recent developments in fabrication of van der Waals heterostructures enable new type devices assembled by stacking atomically thin layers two-dimensional materials. Using this approach, we fabricate light-emitting based on a monolayer WSe2, and also comprising boron nitride tunnelling barriers graphene electrodes, observe sharp luminescence spectra from individual defects WSe2 under both optical electrical excitation. This paves the way towards realisation electrically-pumped quantum...
Resonantly driven quantum emitters offer a very promising route to obtain highly coherent sources of single photons required for applications in information processing (QIP). Realizing this on-chip scalable devices would be important scientific advances and practical the field integrated optics. Here we report dot (QD) resonance fluorescence (RF) efficiently coupled into single-mode waveguide, key component photonic circuit, with negligible resonant laser background show that QD coherence is...
Abstract Quantum states of light and matter can be manipulated on the nanoscale to provide a technological resource for aiding implementation scalable photonic quantum technologies. Experimental progress relies quality efficiency coupling between photons internal spin emitters. Here we demonstrate nanophotonic waveguide platform with embedded dots (QDs) that enables both Purcell-enhanced emission strong chiral coupling. The design uses slow-light effects in glide-plane crystal QD tuning...
Abstract Rydberg excitons (analogues of atoms in condensed matter systems) are highly excited bound electron-hole states with large Bohr radii. The interaction between them as well exciton coupling to light may lead strong optical nonlinearity, applications sensing and quantum information processing. Here, we achieve effective photon–photon interactions (Kerr-like nonlinearity) via the blockade phenomenon hybridisation photons forming polaritons a Cu2O-filled microresonator. Under pulsed...
We demonstrate that efficient optical pumping of nuclear spins in semiconductor quantum dots (QDs) can be achieved by resonant optically forbidden transitions. This process corresponds to one-to-one conversion a photon absorbed the dot into polarized spin, and also has potential for initialization hole spin QDs. find employing this spin-forbidden process, polarization 65% achieved, markedly higher than from allowed transition, which saturates due low probability electron-nuclear flip-flop.
We present a method to implement 3-dimensional polariton confinement with in-situ spectral tuning of the cavity mode. Our tunable microcavity is hybrid system consisting bottom semiconductor distributed Bragg reflector (DBR) containing quantum wells (QWs) grown on top and dielectric concave DBR separated by micrometer sized gap. Nanopositioners allow independent positioning two mirrors mode energy can be tuned controlling distance between them. When close resonance, we observe characteristic...
The fine structure splitting of bright exciton states is measured for a range thermally annealed InGaAs quantum dot (QD) samples with differing degrees $\mathrm{In}∕\mathrm{Ga}$ intermixing and also dot-in-a-well (DWELL) structure. Magnitudes the are determined in polarization-resolved differential transmission experiments from measurements period beats observed QD dynamics. found to decrease structures weaker strain: both intermixed QD's dots surrounded by strain-reducing layers (DWELL's)....
The temperature dependence of spin coherence in InGaAs quantum dots is obtained from beats observed polarization-resolved pump-probe experiments. Within the same sample we clearly distinguish between coherent dynamics leading to and incoherent long-lived spin-memory effects. Analysis data using a theoretical model reveals approximately 10 times greater stability at high compared that found previously for exciton states four-wave-mixing experiments by Borri et al. [Phys. Rev. Lett. 87, 157401...
The potential for scale-up coupled with minimized system size is likely to be a major determining factor in the realization of applicable quantum information systems. Nanofabrication technology utilizing III-V semiconductor provides path scalable bit (qubit) integration and materials platform combined electronic/photonic functionality. Here, we address key requirement qubit-site emission energy control by demonstrating uniform arrays nanowires, where each nanowire contains single dot....
We demonstrate a scheme for in-plane initialization of single exciton spin in an InGaAs quantum dot (QD) coupled to GaAs nanobeam waveguide. The chiral coupling the QD and optical mode enables fidelity approaching unity magnetic field $B=1$ T $>0.9$ without field. further show that this excitation is independent incident laser polarization depends solely on direction. This provides robust basis photon-mediated network information applications.
We report strongly non-reciprocal behaviour for quantum dot exciton spins coupled to nano-photonic waveguides under resonant laser excitation. A clear dependence of the transmission spectrum on propagation direction is found a chirally-coupled dot, with spin up and down coupling left right directions respectively. The reflection signal shows an opposite trend transmission, which numerical model indicates due direction-selective saturation dot. chiral spin-photon interface we demonstrate...
The nature of the nano-scale environment presents a major challenge for solid-state implementation spin-based qubits. In this work, single electron spin in an optically pumped nanometer-sized III-V semiconductor quantum dot is used to control macroscopic nuclear several thousand nuclei, freezing its decay and leading life-times exceeding 100 seconds at low temperatures. Few-millisecond-fast optical initialization followed by slow exhibiting random telegraph signals long delay times, arising...
A demonstration of the principles quantum key distribution is performed using a single-photon source in proof concept test-bed over distance 2 km standard telecommunications optical fiber. The was an optically-pumped dot microcavity emitting at wavelength 895 nm. Characterization parameters range different excitation powers. An investigation effect varying power on bit error rate and cryptographic exchange system are presented.
Nuclear spin polarization dynamics are measured in optically pumped individual $\text{GaAs}/{\text{Al}}_{x}{\text{Ga}}_{1\ensuremath{-}x}\text{As}$ interface quantum dots by detecting the time dependence of Overhauser shift photoluminescence spectra. Long nuclear decay times $\ensuremath{\approx}1\text{ }\text{min}$ have been found indicating inefficient diffusion from GaAs dot into surrounding AlGaAs matrix externally applied magnetic field. A spin-diffusion coefficient two orders lower...
Sizable nuclear spin polarization is pumped in individual electron-charged $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{In}\mathrm{P}$ dots a wide range of external magnetic fields ${B}_{Z}=0--5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ by circularly polarized optical excitation. We observe up to $\ensuremath{\approx}40%$ at ${B}_{Z}=1.5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ corresponding an Overhauser field $\ensuremath{\approx}1.2\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. find strong feedback the on...
Nuclear polarization dynamics are measured in the nuclear spin bistability regime a single optically pumped $\mathrm{In}\mathrm{Ga}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ quantum dot. The controlling role of diffusion from dot into surrounding material is revealed pump-probe measurements nonlinear dynamics. We measure decay times range $0.2--5\phantom{\rule{0.3em}{0ex}}\mathrm{s}$, strongly dependent on optical pumping time. long arises by for $(>5\phantom{\rule{0.3em}{0ex}}\mathrm{s})$...
Microcavity polaritons are strongly interacting hybrid light–matter quasiparticles, which promising for the development of novel light sources and active photonic devices. Here, we report polariton lasing in UV spectral range microring resonators based on GaN/AlGaN slab waveguides, with experiments carried out from 4 K up to room temperature. Stimulated relaxation into multiple ring resonator modes is observed, exhibit threshold-like dependence emission intensity pulse energy. The strong...
We report optically detected nuclear magnetic resonance (ODNMR) measurements on small ensembles of spins in single GaAs quantum dots. Using ODNMR we make direct the inhomogeneous Knight field from a photoexcited electron which acts nuclei dot. The resulting shifts NMR peak can be controlled by varying occupancy and its spin orientation, lead to strongly asymmetric line shapes at high optical excitation. all-optical control shape will enable position-selective groups inside
We use a femtowatt focused laser beam to locate and manipulate single quantum tunneling channel associated with an individual InAs dot within ensemble of dots. The intensity the directed tunes current through targeted effective optical gain ${10}^{7}$ modifies curvature dot's confining potential spatial extent its ground state electron eigenfunction. These observations are explained by effect photocreated hole charges which become bound close dot, thus acting as optically induced gate electrode.
We demonstrate nuclear spin pumping in a single InGaAs∕GaAs dot embedded p-i-n diode the regime of resonant optical excitation spin-polarized electron-hole pairs lowest energy states dot. A mechanism is proposed relevant to high electric field where carriers escape from by tunneling. The degree polarization shown increase strongly with applied field, controlling carrier tunneling dot, since at low fields blocked for re-excitation due slow hole escape.