Accessing higher order correlations by time-multiplexing

We experimentally measured higher order normalized correlation functions (nCF) of pulsed light with a time-multiplexing-detector. We demonstrate excellent performance of our device by verifying unity valued nCF up to the eighth order for coherent light, and factorial dependence of the nCF for pseudothermal light. We applied our measurement technique to a type-II parametric downconversion source to investigate mutual two-mode correlation properties and ascertain nonclassicality.Comment: 5 pages, 3 figure

Direct probing of the Wigner function by time-multiplexed detection of photon statistics

We investigate the capabilities of loss-tolerant quantum state characterization using a photon-number resolving, time-multiplexed detector (TMD). We employ the idea of probing the Wigner function point-by-point in phase space via photon parity measurements and displacement operations, replacing the conventional homodyne tomography. Our emphasis lies on reconstructing the Wigner function of non-Gaussian Fock states with highly negative values in a scheme that is based on a realistic experimental setup. In order to establish the concept of loss-tolerance for state characterization we show how losses can be decoupled from the impact of other experimental imperfections, i.e. the non-unity transmittance of the displacement beamsplitter and non-ideal mode overlap. We relate the experimentally accessible parameters to effective ones that are needed for an optimised state reconstruction. The feasibility of our approach is tested by Monte Carlo simulations, which provide bounds resulting from statistical errors that are due to limited data sets. Our results clearly show that high losses can be accepted for a defined parameter range, and moreover, that (in contrast to homodyne detection) mode mismatch results in a distinct signature, which can be evaluated by analysing the photon number oscillations of the displaced Fock states.Comment: 22 pages, 13 figures, published versio

Variable-range hopping conductivity in La₁₋xCaxMn₁₋yFeyO₃: evidence of a complex gap in density of states near the Fermi level

The resistivity, ρ, of ceramic La₁₋xCaxMn₁₋yFeyO₃ with x = 0.3 and y = 0.0–0.09 is found to obey, between a temperature Tv ≈ 310–330 K and the ferromagnetic-to-paramagnetic transition temperature, Tc = 259–119 K (decreasing with y), the Shklovskii–Efros-type variable-range hopping conductivity law, ρ(T) = ρ₀(T) exp[(T₀/T)¹/₂]. This behaviour is governed by generation of a soft Coulomb gap Δ ≈ 0.42 eV in the density of localized states and a rigid gap δ(T) ≈ δ(Tv)(T/Tv)1/2 with δ(Tv) ≈ 0.16, 0.13 and 0.12 eV at y = 0.03, 0.07 and 0.09, respectively. Deviations from the square root dependence of δ(T), decreasing when y is increased, are observed as T → TC. The prefactor of the resistivity follows the law ρ₀ (T) ~ Tm, where m changes from 9/2 at y = 0 to 5/2 in the investigated samples with y = 0.03, 0.07 and 0.09, which is connected to introduction of an additional fluctuating short-range potential by doping with FeyesBelgorod State Universit

Modally Resolved Fabry-Perot Experiment with Semiconductor Waveguides

Based on the interaction between different spatial modes, semiconductor Bragg-reflection waveguides provide a highly functional platform for non-linear optics. Therefore, the control and engineering of the properties of each spatial mode is essential. Despite the multimodeness of our waveguide, the well-established Fabry-Perot technique for recording fringes in the optical transmission spectrum can successfully be employed for a detailed linear optical characterization when combined with Fourier analysis. A prerequisite for the modal sensitivity is a finely resolved transmission spectrum that is recorded over a broad frequency band. Our results highlight how the features of different spatial modes, such as their loss characteristics and dispersion properties, can be separated from each other allowing their comparison. The mode-resolved measurements are important for optimizing the performance of such multimode waveguides by tailoring the properties of their spatial modes.Comment: 8 pages, 7 figure

Magnetization and Shubnikov-de Haas effect in diluted magnetic semiconductors (Cd₁₋x₋yZnxMny)₃As₂

Presents the results of the Shubnikov-de Haas (SdH) effect and magnetization of single crystals of (Cd1-x-yZnxMny)3As2 magnetic semiconductors. Analysis of SdH oscillations; Exchange constant in the conduction band and spin-dependent part of the Dingle temperatureyesBelgorod State Universit

Producing high fidelity single photons with optimal brightness via waveguided parametric down-conversion

Parametric down-conversion (PDC) offers the possibility to control the fabrication of non-Gaussian states such as Fock states. However, in conventional PDC sources energy and momentum conservation introduce strict frequency and photon number correlations, which impact the fidelity of the prepared state. In our work we optimize the preparation of single-photon Fock states from the emission of waveguided PDC via spectral filtering. We study the effect of correlations via photon number resolving detection and quantum interference. Our measurements show how the reduction of mixedness due to filtering can be evaluated. Interfering the prepared photon with a coherent state we establish an experimentally measured fidelity of the produced target state of 78%.Comment: 15 pages, 10 Figures, published versio

Magnetic MnAs nanoclusters in the diluted magnetic semiconductor (Zn₁₋xMnx)₃As₂

In this work magnetic properties of ZMA are investigated for x= 0.08, 0.10 and 0.13. The dependences of the magnetization on the temperature and magnetic field give evidence for the presence of two magnetic subsystems, PM centres and FM MnAs nanoclusters, in this materialyesBelgorod State Universit

XPS and FTIR study of the influence of electrode potential on activation of pyrite by copper or lead

Activation of pyrite by either copper or lead ions and subsequent xanthate adsorption on activated surfaces were studied in aqueous solutions of pH 5, 6.5 and 9 under different electrochemical conditions using X-ray Photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). At pH 5, the copper concentration on the surface of pyrite increased strongly when the electrode potential was changed towards cathodic direction. At low activation potentials (E-h less than or equal to + 100 mV), a change in the chemical state of sulfur on the surface was observed by XPS proposing formation of a copper-containing surface sulfide phase. In electrochemically-controlled xanthate adsorption, the behavior of copper-activated pyrite resembled that of chalcopyrite (CuFeS2). The results indicate that activation of pyrite by copper at pH 5 can be controlled by the potential of the mineral. At pH 9. the copper content on the surface was independent of the potential of pyrite and no changes were observed in chemical state of sulfur if compared to unactivated pyrite in the potential region - 100 to + 400 mV (SHE). In the case of pyrite activation by lead, no changes were observed in sulfur spectra at either pH 5 or 9 at different electrode potentials. The concentration of lead on the surface increased at pH 5 when potential was changed towards cathodic direction. All lead present at the surface of pyrite was concluded to be in the form of lead(II)-oxygen species and no evidence of exchange between lead and iron was found. Both adsorbed xanthate and dixanthogen were observed on the surface of Cu-activated pyrite after activation at cathodic potentials (- 100 to + 50 mV) and subsequent treatment in either ethyl or amyl xanthate solution of pH 5 or 6.5 at potential region + 350 to 550 mV (standard hydrogen electrode, SHE). In a similar experiments with Pb-activated pyrite, only a faint indication of the adsorbed collector species was found proposing that lead rather depresses than activates pyrite. (C) 1999 Elsevier Science B.V. All rights reserved

Magnetic properties of the new diluted magnetic semiconductor Zn₁₋ₓMnₓAs₂: evidence of MnAs clusters

The preparation and magnetic properties of the diluted magnetic semiconductor Zn₁₋ₓMnₓAs₂, opening a novel group of II–V₂ compounds alloyed with transition metal elements, are reported for the first timeyesBelgorod State Universit