A5062252706- 2D Materials and Applications
- Quantum Computing Algorithms and Architecture
- Quantum Information and Cryptography
- Perovskite Materials and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Plasmonic and Surface Plasmon Research
- Quantum many-body systems
- Strong Light-Matter Interactions
- Molecular Junctions and Nanostructures
- Quantum and electron transport phenomena
- Neural Networks and Reservoir Computing
- Quantum Dots Synthesis And Properties
- Mechanical and Optical Resonators
- Semiconductor Quantum Structures and Devices
- Nanowire Synthesis and Applications
- Metamaterials and Metasurfaces Applications
- Spectroscopy and Quantum Chemical Studies
- Electronic and Structural Properties of Oxides
- Magnetic properties of thin films
- Adaptive optics and wavefront sensing
- Chalcogenide Semiconductor Thin Films
- Photonic and Optical Devices
- Magnetic Properties and Applications
- Quantum, superfluid, helium dynamics
- Semiconductor materials and devices
Hochschule Bonn-Rhein-Sieg
2025
Max Planck Institute of Quantum Optics
2021-2024
Munich Center for Quantum Science and Technology
2023-2024
QuEra Computing (United States)
2023-2024
Harvard University
2015-2022
EXUS (United Kingdom)
2009
IBM (United States)
1966
We consider light scattering off a two-dimensional (2D) dipolar array and show how it can be tailored by properly choosing the lattice constant of order incident wavelength. In particular, we demonstrate that such arrays operate as nearly perfect mirror for wide range angles frequencies, shape emission pattern from an individual quantum emitter into well-defined, collimated beam. These results understood in terms cooperative resonances surface modes supported 2D array. Experimental...
We demonstrate that a single layer of MoSe_{2} encapsulated by hexagonal boron nitride can act as an electrically switchable mirror at cryogenic temperatures, reflecting up to 85% incident light the excitonic resonance. This high reflectance is direct consequence excellent coherence properties excitons in this atomically thin semiconductor. show monolayer exhibits power-and wavelength-dependent nonlinearities stem from exciton-based lattice heating case continuous-wave excitation and...
Excitons in semiconductors, bound pairs of excited electrons and holes, can form the basis for new classes quantum optoelectronic devices. A van der Waals heterostructure built from atomically thin semiconducting transition metal dichalcogenides (TMDs) enables formation excitons holes distinct layers, producing interlayer with large binding energy a long lifetime. Employing heterostructures monolayer TMDs, we realize optical electrical generation long-lived neutral charged excitons. We...
The twist degree of freedom provides a powerful new tool for engineering the electrical and optical properties van der Waals heterostructures. Here, we show that angle can be used to control spin-valley transition metal dichalcogenide bilayers by changing momentum alignment valleys in two layers. Specifically, observe interlayer excitons twisted WSe$_2$/WSe$_2$ exhibit high (>60%) circular polarization (DOCP) long valley lifetimes (>40 ns) at zero electric magnetic fields. lifetime tuned...
We demonstrate a new approach for dynamically manipulating the optical response of an atomically thin semiconductor, monolayer MoSe2, by suspending it over metallic mirror. First, we show that suspended van der Waals heterostructures incorporating MoSe2 host spatially homogeneous, lifetime-broadened excitons. Then, interface this nearly ideal excitonic system with mirror and control exciton-photon coupling. Specifically, electromechanically changing distance between heterostructure mirror,...
Recent progress in the development of quantum technologies has enabled direct investigation dynamics increasingly complex many-body systems. This motivates study complexity classical algorithms for this problem order to benchmark simulators and delineate regime advantage. Here, we present approximating local observables nonlocal quantities such as Loschmidt echo, where evolution is governed by a Hamiltonian. For short times, their computational cost scales polynomially with system size...
Classical optimization problems can be solved by adiabatically preparing the ground state of a quantum Hamiltonian that encodes problem. The performance this approach is determined smallest gap encountered during evolution. Here, we consider maximum independent set problem, which efficiently encoded in describing Rydberg atom array. We present general construction instances problem for minimum decays superexponentially with system size, implying large time to solution via adiabatic small...
We investigate two-dimensional atomic arrays as a platform to modify the electromagnetic environment of individual quantum emitters. Specifically, we demonstrate that control over emission linewidths, resonant frequency shifts, and local enhancement driving fields is possible due strong dipole-dipole interactions within ordered, subwavelength atom configurations. these effects can be used dramatically enhance coherent between distant emitters an array. Possible experimental realizations...
We show that a nonlinear optical response associated with resonant, atomically thin material can be dramatically enhanced by placing it in front of partially reflecting mirror, rendering otherwise weakly systems suitable for experiments and applications involving quantum optics. Our approach exploits the long-lived polariton resonances arise at particular distances between mirror. The scheme is entirely based on free-space optics, eliminating need cavities or complex nanophotonic structures....
We realize a new electroplasmonic switch based upon electrically tunable exciton–plasmon interactions. The device consists of hexagonal boron nitride (hBN)-encapsulated tungsten diselenide (WSe2) monolayer on top single-crystalline silver substrate. ultrasmooth substrate serves dual role as the medium to support surface plasmon polaritons (SPPs) and bottom gate electrode tune WSe2 exciton energy brightness through electrostatic doping. To enhance coupling, we implement plasmonic crystal...
Excitons are composite bosons that can feature spin singlet and triplet states. In usual semiconductors, without an additional spin-flip mechanism, excitons extremely inefficient optical emitters. Transition metal dichalcogenides (TMDs), with their large spin-orbit coupling, have been of special interest for valleytronic applications coupling circularly polarized light to selective valley spin$^{1-4}$. atomically thin MoSe$_2$/WSe$_2$ TMD van der Waals (vdW) heterostructures, the unique...
Quantum simulation is one of the most promising scientific applications quantum computers. Due to decoherence and noise in current devices, it however challenging perform digital a regime that intractable with classical In this work, we propose an experimental protocol for probing dynamics equilibrium properties on near-term As key ingredient our show possible study thermalization even relatively coarse Trotter decomposition Hamiltonian evolution interest. Even though step size too large...
Domain wall creeping in thin magnetic Ni-Fe films has been studied as a function of the film thickness, field pulse amplitude, duration and repetition frequency, bias fields hard direction. The experimental results are reviewed compared with three existing theories, which ascribe to a) Bloch line motion, b) structure changes, c) changing charges along walls, respectively. Based on first theory, methods indicated by reduction creep sensitivity might be obtained.
Efficient sampling from a classical Gibbs distribution is an important computational problem with applications ranging statistical physics over Monte Carlo and optimization algorithms to machine learning. We introduce family of quantum that provide unbiased samples by preparing state encoding the entire distribution. show this approach leads speedup Markov chain algorithm for several examples, including Ising model weighted independent sets two different graphs. Our connects complexity phase...
Many quantum algorithms rely on the measurement of complex amplitudes. Standard approaches to obtain phase information, such as Hadamard test, give rise large overheads due need for global controlled-unitary operations. We introduce a algorithm based analysis that overcomes this problem amplitudes are continuous function time. Our method only requires implementation real-time evolution and shallow circuit approximates short imaginary-time evolution. show outperforms test in terms depth it is...
Adiabatic quantum algorithms represent a promising approach to universal computation. In isolated systems, key limitation such is the presence of avoided level crossings, where gaps become extremely small. open fundamental robustness adiabatic remains unresolved. Here, we study dynamics near an crossing associated with search algorithm, when system coupled generic environment. At zero temperature, find that algorithm scalable provided noise spectral density environment decays sufficiently...
Techniques to mold the flow of light on subwavelength scales enable fundamentally new optical systems and device applications. The realization programmable, active with fast, tunable components is among outstanding challenges in field. Here, we experimentally demonstrate a few-pixel beam steering based electrostatic gate control excitons an atomically thin semiconductor strong light-matter interactions. By combining high reflectivity MoSe2 monolayer graphene split-gate geometry, shape...
Optically generated excitons dictate the absorption and emission spectrum of doped semiconductor transition-metal dichalcogenide monolayers. We show that upon increasing electron density, elementary optical excitations develop a rotonlike dispersion, evidenced by shift lowest-energy state to finite momentum on order Fermi momentum. This effect emerges due Pauli exclusion between sea, but robustness roton minimum in these systems is direct consequence long-range nature Coulomb interaction...