Modulation Transfer Function (MTF) measurement techniques for lenses and linear detector arrays

Application is the determination of the Modulation Transfer Function (MTF) for linear detector arrays. A system set up requires knowledge of the MTF of the imaging lens. Procedure for this measurement is described for standard optical lab equipment. Given this information, various possible approaches to MTF measurement for linear arrays is described. The knife edge method is then described in detail

Variability of gully erosion in a small catchment in South-west Spain

Research on gully erosion is carried out as part of an investigation on erosional and hydrological processes in a small catchment in Extremadura, Spain. The amount of gully erosion is estimated by repeated monitonng of transverse sections since summer 1990. Data obtained so far indicate high spatial and temporal variability. High amounts of erosion are related to a channel section with active headcut retreat, whereas net accumulation occurs where the gully is already deep and wide. Present erosion, apart from headcut retreat, is related to lateral undercutting of the channel bank and bank collapsing. Temporal variability is related with rainfall characteristics and discharge production in the channel. Important sediment losses are produced by highly intensive storms. The most important gully process in the area is shown to be related with the erosive force of flowing surface waters. Furthermore it is discussed whether present active erosion is related to abandonment of cereal cultivation in parts of the catchment about 30 years ago. It is thought that reduced soil erosion on hillslopes due to the change in landuse, and hence lower sediment supply to the channel in the last decades increased gullying

Experimental characterization of Gaussian quantum communication channels

We present a full experimental characterization of continuous variable quantum communication channels established by shared entanglement together with local operations and classical communication. The resulting teleportation channel was fully characterized by measuring all elements of the covariance matrix of the shared two-mode squeezed Gaussian state. From the experimental data we determined the lower bound to the quantum channel capacity, the teleportation fidelity of coherent states and the logarithmic negativity and the purity of the shared state. Additionally, a positive secret key rate was obtained for two of the established channels.Comment: 9 pages, 4 figures, submitted to Physical Review

Towards Einstein-Podolsky-Rosen quantum channel multiplexing

A single broadband squeezed field constitutes a quantum communication resource that is sufficient for the realization of a large number N of quantum channels based on distributed Einstein-Podolsky-Rosen (EPR) entangled states. Each channel can serve as a resource for, e.g. independent quantum key distribution or teleportation protocols. N-fold channel multiplexing can be realized by accessing 2N squeezed modes at different Fourier frequencies. We report on the experimental implementation of the N=1 case through the interference of two squeezed states, extracted from a single broadband squeezed field, and demonstrate all techniques required for multiplexing (N>1). Quantum channel frequency multiplexing can be used to optimize the exploitation of a broadband squeezed field in a quantum information task. For instance, it is useful if the bandwidth of the squeezed field is larger than the bandwidth of the homodyne detectors. This is currently a typical situation in many experiments with squeezed and two-mode squeezed entangled light.Comment: 4 pages, 4 figures. In the new version we cite recent experimental work bei Mehmet et al., arxiv0909.5386, in order to clarify the motivation of our work and its possible applicatio

Bilateral Gonadal Cysts and Late Diagnosis of Androgen Insensitivity Syndrome Treated by Laparoscopic Gonadectomy

Background. Complete androgen insensitivity syndrome is a rare syndrome in which the uterus is absent and testes rather than ovaries are present. Patients usually visit a gynecologist due to primary amenorrhea. Case. A forty-eight-year-old woman with lower abdominal pain and anamnesis of uterus agenesis was operated on due to bilateral cystic masses. A 5 × 3 × 1.2 cm left adnexal cyst revealed the presence of a serous cyst with a hypoplastic ductus deferens. A smaller cyst of the right adnexa revealed immature testis tissue with Leydig-cell hyperplasia. After karyotype and hormonal examinations, laparoscopic gonadectomy was performed. Conclusion. Attention should be paid in all cyst-removing operations in cases of uterus agenesis, due to the high incidence of malignancy. Not of less importance is the issue of informing the patient in the most appropriate way

Tomographic readout of an opto-mechanical interferometer

The quantum state of light changes its nature when being reflected off a mechanical oscillator due to the latter's susceptibility to radiation pressure. As a result, a coherent state can transform into a squeezed state and can get entangled with the motion of the oscillator. The complete tomographic reconstruction of the state of light requires the ability to readout arbitrary quadratures. Here we demonstrate such a readout by applying a balanced homodyne detector to an interferometric position measurement of a thermally excited high-Q silicon nitride membrane in a Michelson-Sagnac interferometer. A readout noise of \unit{1.9 \cdot 10^{-16}}{\metre/\sqrt{\hertz}} around the membrane's fundamental oscillation mode at \unit{133}{\kilo\hertz} has been achieved, going below the peak value of the standard quantum limit by a factor of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a rather broad frequency range around the mechanical resonance.Comment: 7 pages, 5 figure

An experimental investigation of criteria for continuous variable entanglement

We generate a pair of entangled beams from the interference of two amplitude squeezed beams. The entanglement is quantified in terms of EPR-paradox [Reid88] and inseparability [Duan00] criteria, with observed results of $\Delta^{2} X_{x|y}^{+} \Delta^{2} X_{x|y}^{-} = 0.58 \pm 0.02$ and $\sqrt{\Delta^{2} X_{x \pm y}^{+} \Delta^{2} X_{x \pm y}^{-}} = 0.44 \pm 0.01$, respectively. Both results clearly beat the standard quantum limit of unity. We experimentally analyze the effect of decoherence on each criterion and demonstrate qualitative differences. We also characterize the number of required and excess photons present in the entangled beams and provide contour plots of the efficacy of quantum information protocols in terms of these variables.Comment: 4 pages, 5 figure

Microcanonical entropy inflection points: Key to systematic understanding of transitions in finite systems

We introduce a systematic classification method for the analogs of phase transitions in finite systems. This completely general analysis, which is applicable to any physical system and extends towards the thermodynamic limit, is based on the microcanonical entropy and its energetic derivative, the inverse caloric temperature. Inflection points of this quantity signal cooperative activity and thus serve as distinct indicators of transitions. We demonstrate the power of this method through application to the long-standing problem of liquid-solid transitions in elastic, flexible homopolymers.Comment: 4 pages, 3 figure