A5047665170- Quantum Information and Cryptography
- Quantum optics and atomic interactions
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- Quantum Mechanics and Applications
- Mechanical and Optical Resonators
- Laser-Matter Interactions and Applications
- Quantum Computing Algorithms and Architecture
- Diamond and Carbon-based Materials Research
- Photonic and Optical Devices
- Near-Field Optical Microscopy
- Advanced Fiber Laser Technologies
- Spectroscopy and Laser Applications
- Spectroscopy and Quantum Chemical Studies
- Orbital Angular Momentum in Optics
- Semiconductor Quantum Structures and Devices
- Molecular Junctions and Nanostructures
- Analytical Chemistry and Sensors
- Semiconductor materials and devices
- Strong Light-Matter Interactions
- Chaos-based Image/Signal Encryption
- Advanced Fluorescence Microscopy Techniques
- Electrochemical Analysis and Applications
- Advanced Electron Microscopy Techniques and Applications
- Coding theory and cryptography
Leibniz University Hannover
2022-2023
University of Stuttgart
2010-2022
Center for Integrated Quantum Science and Technology
2014-2021
Max Planck Institute for Solid State Research
2010-2021
University of British Columbia
2011-2013
Max Planck Society
2013
Centre for Quantum Technologies
2007-2012
National University of Singapore
2009-2011
ETH Zurich
2007-2010
École Polytechnique Fédérale de Lausanne
2002-2004
Newly discovered van der Waals materials like MoS2, WSe2, hexagonal boron nitride (h-BN), and recently C2N have sparked intensive research to unveil the quantum behavior associated with their 2D structure. Of great interest are that host single emitters. h-BN, a band gap of 5.95 eV, has been shown emitters which stable at room temperature in UV visible spectral range. In this paper we investigate correlations between h-BN structural features emitter location from bulk down monolayer...
By performing cryogenic laser spectroscopy under a scanning probe electrode that induces local electric field, we have resolved two individual fluorescent molecules separated by 12 nanometers in an organic crystal. The undergo strong coherent dipole-dipole coupling produces entangled sub- and superradiant states. Under intense illumination, both are excited via two-photon transition, the fluorescence from this doubly system displays photon bunching. Our experimental scheme can be used to...
Entanglement witnesses such as Bell inequalities are frequently used to prove the nonclassicality of a light source and its suitability for further tasks. By demonstrating inequality violations using classical in common experimental arrangements, we highlight why strict locality efficiency conditions not optional, particularly security-related scenarios.
Recent efforts to define microscopic solid-immersion-lenses (SIL) by focused ion beam milling into diamond substrates that are registered a preselected single photon emitter summarized. We show how we determine the position of with at least 100 nm lateral and 500 axial accuracy, procedure is optimized. The characteristics emitter, Nitrogen Vacancy (NV) center in diamond, measured before after producing SIL compared each other. A count rate 1.0 × 10(6) counts/s achieved [111] oriented NV center.
Abstract Ultralight bosons such as axion-like particles are viable candidates for dark matter. They can form stable, macroscopic field configurations in the of topological defects that could concentrate matter density into many distinct, compact spatial regions small compared with Galaxy but much larger than Earth. Here we report results search transient signals from domain walls by using global network optical magnetometers exotic (GNOME) physics searches. We data, consisting correlated...
We present an experiment where a single molecule strongly affects the amplitude and phase of laser field emerging from subwavelength aperture. achieve visibility -6% in direct +10% cross-polarized detection schemes. Our analysis shows that close to full extinction should be possible using near-field excitation.
In this work, we experimentally demonstrate a novel and simple approach that uses off-the-shelf optical elements to enhance the collection efficiency from single emitter. The key component is solid immersion lens made of diamond, host material for color centers. We improve excitation detection emitters by one order magnitude, as predicted theory.
Many quantum key distribution (QKD) implementations using a free space transmission path are restricted to operation at night time in order distinguish the signal photons used for secure establishment from background light. Here, we present lean entanglement-based QKD system overcoming that limitation. By implementing spectral, spatial and temporal filtering techniques, establish continuously over several days under varying light weather conditions.
Abstract Narrow-band optical filtering is required in many spectroscopy applications to suppress unwanted background light. One example quantum communication where the fidelity often limited by performance of filters. This limitation can be circumvented utilizing GHz-wide features a Doppler broadened atomic gas. The anomalous dispersion vapours enables spectral filtering. These, so-called, Faraday filters (FADOFs) far better than any commercial filter terms bandwidth, transition edge and...
Semiconductor defects allowing efficient interaction between spins and photons can serve as building blocks for scalable quantum networks. The silicon vacancy (${V}_{\text{Si}}$) in SiC possesses controllable, long-lived ground-state spins, adjustable fluorescence properties. However, its broad distribution of emitted-photon energies at room temperature means ${V}_{\text{Si}}$'s feasibility needs to be checked liquid-helium temperature, where phonon coupling is suppressed. This study finds a...
Abstract Hybrid quantum systems integrating semiconductor dots (QDs) and atomic vapours become important building blocks for scalable networks due to the complementary strengths of individual parts. QDs provide on-demand single-photon emission with near-unity indistinguishability comprising unprecedented brightness—while vapour ultra-precise frequency standards promise long coherence times storage qubits. Spectral filtering is one key components successful link between QD photons atoms. Here...
We report on the excitation of single molecules via narrow zero-phonon transitions using short laser pulses. By monitoring Stokes-shifted fluorescence, we studied excited state population as a function delay time, intensity, and frequency detuning. A $\ensuremath{\pi}$-pulse was demonstrated with merely 500 photons, 5 Rabi cycles were achieved at higher powers. Our findings are in good agreement theoretical calculations provide first step toward coherent manipulation electronic states few photons.
Future quantum networks will need flying qubits and stationary nodes. As for the generation of single photons which may act as qubits, resonantly excited single-semiconductor dots are ideal in terms their on-demand single-photon emission, indistinguishability, brightness. Atomic systems can effectively mediators photon–photon interactions, storage media, or building blocks qubits. Here, we hybridize these two investigate non-classical interference spectral Lorentzian-shaped photons,...
Single photons exhibit quantum interference behaviors in novel experiments that extend previous characterization techniques, a key step for assessing the utility of single future networks.
The influence of bright light on a single-photon detector has been described in number recent publications. impact quantum key distribution (QKD) is important, and several hacking experiments have tailored to fully control detectors. Special attention given avoid introducing further errors into QKD system. We describe the design technical details an apparatus which allows attack quantum-cryptographic connection. This device capable controlling free-space fiber-based systems minimizing...
Photonic entanglement is one of the key resources in modern quantum optics. It opens door to schemes such as communication, teleportation, and quantum-enhanced precision sensing. Sources based on parametric down-conversion or cascaded decays atomic atom-like emitters are limited because their weak interaction with stationary qubits. This due commonly broadband emission. Furthermore, these sources near-infrared that blue spectral region, ions many defect centers, cannot be addressed. Here, we...
The Macaluso-Corbino effect describes the optical rotation of light in spectral proximity to an atomic resonance. One use this is narrowband filtering. So-called Faraday filters utilize difference two components refractive indices, which are split by Zeeman a longitudinal magnetic field. This allows for net linearly polarized input beam within medium. Placing it between crossed polarizers therefore only near resonance pass. Since any resonant spectrum implies anomalous dispersion on...
Abstract One of the most fundamental quantum random number generators is implemented with light impinging onto a beam splitter, and two single photon detectors at its output. Often, this generator described as “a which takes one or other path towards detector”. The input state in conjunction detector response relevant for amount, pattern, correlation generated clicks. Only fraction all outcomes, min‐entropy, can be used further resource true randomness. This paper addresses difference common...