A5027406567- Quantum optics and atomic interactions
- Quantum Information and Cryptography
- Luminescence Properties of Advanced Materials
- Quantum Mechanics and Applications
- Atomic and Subatomic Physics Research
- Photonic and Optical Devices
- Semiconductor materials and devices
- Radiation Detection and Scintillator Technologies
- Photonic Crystals and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Radiotherapy Techniques
- Nanowire Synthesis and Applications
- Semiconductor materials and interfaces
- Radiation Therapy and Dosimetry
- Semiconductor Quantum Structures and Devices
- Silicon Nanostructures and Photoluminescence
- Quantum and electron transport phenomena
- Quantum Dots Synthesis And Properties
- Advanced Fiber Laser Technologies
- Quantum Computing Algorithms and Architecture
- Diamond and Carbon-based Materials Research
- Nonlinear Optical Materials Studies
- Plasmonic and Surface Plasmon Research
- Photorefractive and Nonlinear Optics
- Luminescence and Fluorescent Materials
Aarhus University
2015-2024
Lundbeck Foundation
2012
Lund University
2009-2010
Technical University of Denmark
2008-2009
Ørsted (Denmark)
2008-2009
National Research Foundation
2008
University of Copenhagen
2007
Danish National Research Foundation
2002-2007
Peter the Great St. Petersburg Polytechnic University
2005
Danish Pain Research Center
2003
We present time-resolved spontaneous emission measurements of single quantum dots embedded in photonic crystal waveguides. Quantum that couple to a waveguide are found decay up 27 times faster than uncoupled dots. From these $\ensuremath{\beta}$-factors 0.89 derived, and an unprecedented large bandwidth 20 nm is demonstrated. This shows the promising potential waveguides for efficient single-photon sources. The scaled frequency range over which enhancement observed excellent agreement with...
We propose a multi-mode quantum memory protocol able to store the state of field in microwave resonator into an ensemble electronic spins. The stored information is protected against inhomogeneous broadening spin by spin-echo techniques resulting times orders magnitude longer than previously achieved. By calculating evolution first and second moments spin-cavity system variables for realistic experimental parameters, we show that based on NV center spins diamond can qubit encoded |0> |1>...
A density matrix ρ(t) yields probabilistic information about the outcome of measurements on a quantum system. We introduce here past state, which, at time T, accounts for state system earlier times t<T. The Ξ(t) is composed two objects, and E(t), conditioned dynamics probing until t in interval [t, T], respectively. characterized by its ability to make better predictions unknown any measurement than conventional that time. On one hand, our formalism shows how smoothing procedures estimation...
Quantum computing promises to tackle computational problems that are intractable with classical computers. Researchers demonstrate spin ensembles can store quantum information over longer times than previously achieved, a significant step toward memory.
The short-circuit behavior of power devices is highly relevant for converter design and fault protection. In this paper, the degradation during short circuit a 10-kV 10-A 4H-SiC MOSFET investigated at 6 kV dc-link voltage. study aims to present device transients as it sustains increasing pulses its lifetime. As pulse length increases, can be observed in periodically performed characterizations. initial seems associated with channel region, continuous stressing leads an overall increase...
Quantum-state tomography is used to characterize the state of an ensemble based qubit implemented through two hyperfine levels in ${\mathrm{Pr}}^{3+}$ ions, doped into a ${\mathrm{Y}}_{2}\mathrm{Si}{\mathrm{O}}_{5}$ crystal. We experimentally verify that single-qubit rotation errors due inhomogeneities can be suppressed using Roos-M\o{}lmer dark-state scheme [Roos and M\o{}lmer, Phys. Rev. A 69, 022321 (2004)] Fidelities above $>90%$, presumably limited by excited decoherence, were achieved....
Long-lived dark exciton states are formed in self-assembled quantum dots due to the combination of angular momentum electrons and holes. The lifetime excitons determined by spin-flip processes that transfer into radiative bright excitons. We employ time-resolved spontaneous emission measurements a modified local density optical unambiguously record rate. Pronounced variations rate with dot energy observed demonstrating storage time can be extended controlling size. dependence is compared...
We report the storage of microwave pulses at single-photon level in a spin-ensemble memory consisting ${10}^{10}$ nitrogen-vacancy centers diamond crystal coupled to superconducting $LC$ resonator. The energy signal, retrieved $100\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$ later by spin-echo techniques, reaches $0.3%$ absorbed spins. This efficiency is quantitatively accounted for simulations. figure merit sufficient envision first implementations quantum qubits.
We report an experiment on mapping a quantum state of light onto the ground spin ensemble Cs atoms with lifetime 2 ms. Recording one two quadrature phase operators is demonstrated vacuum and squeezed states light. The sensitivity procedure at level approximately 1 photon/sec per Hz shown. results pave road towards complete (storing both observables) memory for Gaussian also sheds new fundamental limits magneto-optical resonance method.
A quantum system can be monitored through repeated interactions with meter systems. The state of the at time $t$, represented by density matrix $\ensuremath{\rho}(t)$, then becomes conditioned on information obtained meters until that time. More insight in any $t$ is provided, however, taking into account full detection all interacting both past and future $t$. We present experiments use near-resonant atomic probes to monitor evolution quantized field a cavity. application forward-backward...
This article reviews efforts to build a new type of quantum device, which combines an ensemble electronic spins with long coherence times, and small-scale superconducting processor. The goal is store over times arbitrary qubit states in orthogonal collective modes the spin-ensemble, retrieve them on-demand. We first present protocol devised for such multi-mode memory. then describe series experimental results using NV center diamond, demonstrate its main building blocks: transfer from into...
Radiotherapy is a well-established and important treatment for cancer tumors, advanced technologies can deliver doses in complex three-dimensional geometries tailored to each patient's specific anatomy. A 3D dosimeter, based on optically stimulated luminescence (OSL), could provide high accuracy reusable tool verifying such dose delivery. Nanoparticles of an OSL material embedded transparent matrix have previously been proposed as inexpensive which be read out using laser-based methods....
We present an experimental setup capable of time-resolved photoluminescence spectroscopy for photon energies in the range 0.51 to 0.56 eV with instrument time response 75 ps. The detection system is based on optical parametric three-wave mixing, operates at room temperature, has spectral resolving power, and shown be well suited investigating dynamical processes germanium-tin alloys. In particular, carrier lifetime a direct-bandgap <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Quantum information protocols utilizing atomic ensembles require preparation of a coherent spin state (CSS) the ensemble as an important starting point. We investigate magneto-optical resonance method for characterizing cesium atoms in paraffin coated vapor cell. Atoms constant magnetic field are subject to off-resonant laser beam and RF field. The spectrum Zeeman sub-levels, particular weak quadratic effect, enables us measure orientation, number atoms, transverse coherence time. Notably...
Quantum theoretical treatment of coherent forward scattering light in a polarized atomic ensemble with an arbitrary angular momentum is developed. We consider weak radiation field interacting realistic multi-level transition. Based on the concept effective Hamiltonian and Heisenberg formalism, we discuss coupled dynamics quantum fluctuations polarization Stokes components propagating collective spin atoms. show that process this can be described terms polariton-type wave created sample. Our...
There have recently been several studies of the performance laser frequency stabilization using spectral holes in solids, instead an external cavity, as a reference. Here analytical theory for Pound-Drever-Hall hole-burning is developed. The interaction between atomic medium and phase modulated light described linearized model Maxwell-Bloch equations. interplay carrier modulation sidebands reveals significant differences from case locking to cavity. These include different optimum index,...
In this contribution, we study the optically stimulated luminescence (OSL) exhibited by commercial [Formula: see text]:Ce crystals. This photon emission mechanism, complementary to scintillation, can trap a fraction of radiation energy deposited in material and provides sufficient signal develop novel post-irradiation 3D dose readout. We characterize OSL through spectrally temporally resolved measurements monitor linearity response over broad range. The show that text] centers responsible...
Correlations in photodetection signals from quantum light sources are conventionally calculated by application of the source master equation and regression theorem. In this article we show how conditioned dynamics, associated with theory measurements, allows calculations offers interpretations behavior same quantities. Our is illustrated for photon counting field-amplitude show, particular, transient correlations between measurements later events can be accounted a recently developed past...
In this letter, we present a comparative experimental–simulation study of Au-nanodisc-enhanced upconversion 1500 nm light in an Er3+ doped TiO2 thin film. The geometry the Au nanodiscs was guided by finite-element simulations based on single nanodisc finite computational domain and controlled experimentally using electron-beam lithography. surface-plasmon resonances (SPRs) exhibited well-known spectral red shift with increasing diameter, well explained model. However, observed double-peak...