Shaping frequency entangled qudits

Quantum entanglement between qudits - the d-dimensional version of qubits - is relevant for advanced quantum information processing and provides deeper insights in the nature of quantum correlations. Encoding qudits in the frequency modes of photon pairs produced by continuous parametric down-conversion enables access to high-dimensional states. By shaping the energy spectrum of entangled photons, we demonstrate the creation, characterization and manipulation of entangled qudits with dimension up to 4. Their respective density matrices are reconstructed by quantum state tomography. For qubits and qutrits we additionally measured the dependency of a d-dimensional Bell parameter for various degrees of entanglement. Our experiment demonstrates the ability to investigate the physics of high-dimensional frequency entangled qu$d$it states which are of great importance for quantum information science.Comment: 17 pages, 3 figure

Versatile shaper-assisted discretization of energy-time entangled photons

We demonstrate the capability to discretize the frequency spectrum of broadband energy-time entangled photons by means of a spatial light modulator to encode qudits in various bases. Exemplarily, we implement three different discretization schemes, namely frequency bins, time bins and Schmidt modes. Entangled qudits up to dimension $d=4$ are then revealed by two-photon interference experiments with visibilities violating a $d$-dimensional Bell inequality.Comment: 22 pages, 11 figure

Attitudes langagières de la communauté mohawk de Kahnawake et leur impact sur l’emploi du mohawk de 1971 à 1990

Le but de cet article est de décrire les attitudes des Indiens Mohawks à la réserve de Kahnawake envers les langues mohawk, anglaise et française et leur impact sur l’emploi du mohawk. Il s’agit du résultat d’un projet pilote à deux volets : 1) une enquête menée en 1971 auprès de Mohawks appartenant à différents groupes d’âge; 2) d’une analyse ethnographique de l’impact de ces attitudes en 1990 sur l’emploi du mohawk.The intent of this paper is to outline the attitudes of the Mohawk Indians on the Kahnawake reserve toward English, French and Mohawk and their impact on the use of Mohawk. This article reports on two sets of findings of a pilot study: 1) a cross-generation survey of language attitudes designed in 1971; 2) an ethnographic analysis on the impact of these attitudes on the use of Mohawk in 1990

Extending time-domain ptychography to generalized phase-only transfer functions

We extend the time-domain ptychographic iterative engine to generalized spectral phase-only transfer functions. The modified algorithm, i$^2$PIE, is described and its robustness is demonstrated by different numeric simulations. The concept is experimentally verified by reconstruction of a complex supercontinuum pulse from an all normal dispersion fiber.Comment: 5 pages, 4 figures, submitted to Optic

Dispersion Measurement of Ultra-High Numerical Aperture Fibers covering Thulium, Holmium, and Erbium Emission Wavelengths

We present broadband group velocity dispersion (GVD) measurements of commercially available ultra-high numerical aperture fibers (UHNA1, UHNA3, UHNA4, UHNA7 and PM2000D from Coherent-Nufern). Although these fibers are attractive for dispersion management in ultrafast fiber laser systems in the 2 {\mu}m wavelength region, experimental dispersion data in literature is scarce and inconsistent. Here we demonstrate the measurements using the spectral interferometry technique covering the typically used erbium, thulium and holmium emission bands. The results are characterized in terms of the standard-deviation uncertainty and compared with previous literature reports. Fitting parameters are provided for each fiber allowing for the straightforward replication of the measured dispersion profiles. This work is intended to facilitate the design of ultrafast fiber laser sources and the investigations of nonlinear optical phenomena

Tuning curve of type-0 spontaneous parametric down-conversion

We study the tuning curve of entangled photons generated by type-0 spontaneous parametric down-conversion in a periodically poled KTP crystal. We demonstrate the X-shaped spatiotemporal structure of the spectrum by means of measurements and numerical simulations. Experiments for different pump waists, crystal temperatures, and crystal lengths are in good agreement with numerical simulations.Comment: 7 pages, 6 figure

Ecosystem services for communities in forest frontiers: An assessment of nature’s benefits to local stakeholders under different land use and tenure systems in a tropical frontier landscape in Myanmar

Tropical forest frontier landscapes are subject to land use changes and different claims on land by various actors, often leading to trade-offs and a general decline in ecosystem services (ES) for local communities. However, few comprehensive ES studies have been done in such data-scarce frontier regions and they are limited in terms of area, land uses, and number and types of ES assessed. This doctoral thesis aimed to analyse how local stakeholders in Myanmar’s Tanintharyi Region can benefit from various ES and how these are associated to different factors such as land use, land tenure, market access, or population structures. Applying advanced modelling techniques, I used Bayesian networks to model the supply, demand, flow and final outcomes of nine ES: subsistence foods, commercial products, fuelwood, medicinal plants, biodiversity, climate regulation, water regulation, environmental education, and cultural identity. The models were developed in an iterative process and integrated existing spatial datasets, census data and qualitative data from focus group discussions and interviews with local communities, government representatives, researchers, civil society organizations and non-governmental institutions working on land issues in Tanintharyi. I linked the nine models to spatial data to map ES supply, demand, and flow for local stakeholders across the region. Finally, I combined these maps to identify supply/demand (mis)matches as well as accessibility that particularly affects local communities. The thesis highlights the value of mosaic landscapes and the crucial role of equitable land tenure in tropical forest frontiers for providing multiple ES and enhancing human well-being

Time-domain ptychography

Through dedicated measurements in the optical regime we demonstrate that ptychography can be applied to reconstruct complex-valued object functions that vary with time from a sequence of spectral measurements. A probe pulse of approximately 1 ps duration, time delayed in increments of 0.25 ps is shown to recover dynamics on a ten times faster time scale with an experimental limit of approximately 5 fs.Comment: 5 pages, 4 figures, new title and minor text change