Copper oxide and cobalt oxide (CuO, Co3O4) nanocrystals (NCs) have been successfully prepared in a short time using microwave irradiation without any postannealing treatment. Both kinds of nanocrystals (NCs) have been prepared using copper nitrate and cobalt nitrate as the starting materials and distilled water as the solvent. The resulted powders of nanocrystals (NCs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements. The obtained results confirm the presence of the both of oxides nanopowders produced during chemical precipitation using microwave irradiation. A strong emission under UV excitation is obtained from the prepared CuO and Co3O4nanoparticles. The results show that the nanoparticles have high dispersion and narrow size distribution. The line scans of atomic force microscopy (AFM) images of the nanocrystals (NCs) sprayed on GaAs substrates confirm the results of both X-ray diffraction and transmission electron microscopy. Furthermore, vibrational studies have been carried out using Raman spectroscopic technique. Specific Raman peaks have been observed in the CuO and Co3O4nanostructures, and the full width at half maximum (FWHM) of the peaks indicates a small particle size of the nanocrystals.

We demonstrate quantum interference between photons generated by the radiative decay processes of excitons that are bound to isolated fluorine donor impurities in ZnSe/ZnMgSe quantum-well nanostructures. The ability to generate single photons from these devices is confirmed by autocorrelation experiments, and the indistinguishability of photons emitted from two independent nanostructures is confirmed via a Hong-Ou-Mandel dip. These results indicate that donor impurities in appropriately engineered semiconductor structures can portray atomlike homogeneity and coherence properties, potentially enabling scalable technologies for future large-scale optical quantum computers and quantum communication networks.

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Zinc bis(chelate) guanidine complexes promote living lactide polymerization at elevated temperatures. By means of kinetic and spectroscopic analyses the mechanism has been elucidated for these special initiators that make use of neutral N-donor ligands. The neutral guanidine function initiates the polymerization by a nucleophilic ring-opening attack on the lactide molecule. DFT calculations on the first ring-opening step show that the guanidine is able to act as a nucleophile. Three transition states were located for ligand rearrangement, nucleophilic attack, and ring-opening. The second ring-opening step was modeled as a representation for the chain growth because here, the lactate alcoholate opens the second lactide molecule via two transition states (nucleophilic attack and ring-opening). Additionally, the resulting reaction profile proceeds overall exothermically, which is the driving force for the reaction. The experimental and calculated data are in good agreement and the presented mechanism explains why the polymerization proceeds without co-initiators.

The spin dynamics of the strongly localized, donor-bound electrons in fluorine-doped ZnSe epilayers is studied by pump-probe Kerr rotation techniques. A method exploiting the spin inertia is developed and used to measure the longitudinal spin relaxation time, T1, in a wide range of magnetic fields, temperatures, and pump densities. The T1 time of the donor-bound electron spin of about 1.6 µs remains nearly constant for external magnetic fields varied from zero up to 2.5 T (Faraday geometry) and in a temperature range 1.8 − 45 K. The inhomogeneous spin dephasing time, T * 2 = 8 − 33 ns, is measured using the resonant spin amplification and Hanle effects under pulsed and steady-state pumping, respectively. These findings impose severe restrictions on possible spin relaxation mechanisms.

We report on the optical investigation of single electron spins bound to fluorine donor impurities in ZnSe. Measurements of photon antibunching establish the presence of single, isolated optical emitters, and magnetooptical studies are consistent with the presence of an exciton bound to the spin-impurity complex. The isolation of this single donor-bound exciton complex and its potential homogeneity offer promising prospects for a scalable semiconductor qubit with an optical interface.PACS numbers: 78.55. Et, Schemes for quantum information processing and quantum communications rely on scalable, robust qubits. In particular, there are many proposals that require fast, efficient, and homogenous single-photon sources 1-3 and still others that rely on the interaction between matter qubits and flying photonic qubits 4 . The requisites for both types of schemes can be satisfied with semiconductor electron spins, which serve as single photon sources 5 or long lived quantum memories with an optical interface 6-8 . However, optical schemes, particularly those based on entanglement, also require large numbers of homogenous photon emitters 9-14 . Electron spins in self-assembled QDs, unfortunately, suffer from large inhomogenities due to their natural size distribution.Impurity-bound electrons in direct bandgap semiconductors, however, have relatively little inhomogeneous broadening 15-20 , yet still possess strong optical transitions when binding an additional exciton 18-21 and long ground state coherence times 7 .An electron bound to a single fluorine donor in ZnSe (F:ZnSe) may serve as a physical qubit with many potential advantages over previously researched qubits. F:ZnSe is particularly appealing because of its nuclear structure compared to III-V-based bound-exciton or quantum dot systems. Unlike III-V systems, isotopic purification of the ZnSe-host matrix to a nuclear-spin-0 background is possible, eliminating magnetic noise from nuclear spin diffusion 22,23 . Further, the F-impurity has a nuclear spin of 1/2 with 100% abundance. Electronnuclear spin swapping schemes 24,25 can be used, which, in combination with the spin-0 background of the isotopically purified host matrix, could lead to an extremely long-lived qubit. Additionally, the applicability of standard microfabrication techniques 26,27 to ZnSe makes the F:ZnSe system particularly scalable.The F:ZnSe system has already shown promise as a scalable source of single photons in Ref. 20. However, a) Electronic address: kdegreve@stanford.edu b) Currently at HRL Laboratories, LLC, 3011 Malibu Canyon Rd., Malibu, CA 90265.this work did not demonstrate the potential of the donor system as a future quantum memory. Here, we show both statistics for single photon emission, as well as the presence of a three-level optical Λ-system through magnetospectroscopy experiments. This introduces F:ZnSe as a valid candidate for use as a scalable qubit with an optical interface.~ 23 meV TES I 2 FE-LH FE-HH c) pump D 0 X D 0 1s 2s,2p I 2 2s-TES 21 meV b) Zn 0.92 Mg 0.08 Se Zn 0.92 M...

We demonstrate laser emission from optically pumped non-polar cubic GaN quantum dots embedded in cubic aluminum nitride microdisks. Power dependent micro-photoluminescence studies at low temperature (∼10 K) revealed S-shaped curves of the integral mode intensity. We observed whispering gallery modes with quality factors up to 5000 at the high energy side (4 eV, i.e., ∼310 nm wavelength) in photoluminescence spectra of microdisks with a diameter of 2.5 μm. Furthermore, we have determined the spontaneous emission coupling factors to β = 0.12 and β = 0.42 for resonator modes of different radial orders.

Here we demonstrate optical pumping of a single electron within a semiconductor nanostructure comprised of a single fluorine donor located within a ZnSe/ZnMgSe quantum well. Experiments were performed to detect optical pumping behavior by observing single photons emitted from the nanostructure when the electron changes spin state. These results demonstrate initialization and read-out of the electron spin qubit and open the door for coherent optical manipulation of a spin by taking advantage of an unconventional nanostructure.