Testing Ultrafast Two-Photon Spectral Amplitudes via Optical Fibres

We test two-dimensional TPSA of biphoton light emitted via ultrafast spontaneous parametric down-conversion (SPDC) using the effect of group-velocity dispersion in optical fibres. Further, we apply this technique to demonstrate the engineering of biphoton spectral properties by acting on the pump pulse shape

Experimental realization of a low-noise heralded single photon source

We present a heralded single-photon source with a much lower level of unwanted background photons in the output channel by using the herald photon to control a shutter in the heralded channel. The shutter is implemented using a simple field programable gate array controlled optical switch.Comment: 4 pages, 5 figure

The time as an emergent property of quantum mechanics, a synthetic description of a first experimental approach

The "problem of time" in present physics substantially consists in the fact that a straightforward quantization of the general relativistic evolution equation and constraints generates for the Universe wave function the Wheeler-De Witt equation, which describes a static Universe. Page and Wootters considered the fact that there exist states of a system composed by entangled subsystems that are stationary, but one can interpret the component subsystems as evolving: this leads them to suppose that the global state of the universe can be envisaged as one of this static entangled state, whereas the state of the subsystems can evolve. Here we synthetically present an experiment, based on PDC polarization entangled photons, that allows showing with a practical example a situation where this idea works, i.e. a subsystem of an entangled state works as a "clock" of another subsystem

Experimental Test of an Event-Based Corpuscular Model Modification as an Alternative to Quantum Mechanics

We present the first experimental test that distinguishes between an event-based corpuscular model (EBCM) [H. De Raedt et al.: J. Comput. Theor. Nanosci. 8 (2011) 1052] of the interaction of photons with matter and quantum mechanics. The test looks at the interference that results as a single photon passes through a Mach-Zehnder interferometer [H. De Raedt et al.: J. Phys. Soc. Jpn. 74 (2005) 16]. The experimental results, obtained with a low-noise single-photon source [G. Brida et al.: Opt. Expr. 19 (2011) 1484], agree with the predictions of standard quantum mechanics with a reduced $\chi^2$ of 0.98 and falsify the EBCM with a reduced $\chi^2$ of greater than 20

Dispersion spreading of biphotons in optical fibres and two-photon interference

We present the first observation of two-photon polarization interference structure in the second-order Glauber's correlation function of two-photon light generated via type-II spontaneous parametric down-conversion. In order to obtain this result, two-photon light is transmitted through an optical fibre and the coincidence distribution is analyzed by means of the START-STOP method. Beyond the experimental demonstration of an interesting effect in quantum optics, these results also have considerable relevance for quantum communications.Comment: Accepted for publication in Phys.Rev.Let

Left Ventricular Hypertrophy in Obese Hypertensives: Is It Really Eccentric? (An Echocardiographic Study)

In order to study left ventricular hypertrophy patterns in obese hypertensives, we examined 132 patients with essential hypertension by 2D, M-mode and Doppler echocardiography. The patients were classified in four comparable groups, corresponding to the values of Quetelet’s body mass index (BMI) and grades of obesity. More obese hypertensives had on average larger left ventricles with thicker walls and larger left atria than less obese, or lean ones. Left ventricular mass increased significantly and progressively with advancing grades of obesity, but relative wall thickness (wall thickness/cavity size ratio) did not diminish. Doppler echocardiography revealed significantly higher prevalence of left ventricular diastolic dysfunction among obese than among lean hypertensives. In the second part of our study, we analyzed the subgroups defined by the severity of hypertension and the age of the patients. The correlation of the indices of left ventricular and left atrial hypertrophy with the BMI values was considerably better in the group of moderate than in the group of mild hypertension. The r values were 0.62 vs. 0.22 for left ventricular mass and 0.64 vs. 0.26 for left atrial dimension. The group of patients with severe hypertension was characterized by left ventricular cavity enlargement in correlation with increasing BMI values, but without corresponding left ventricular wall thickening. So called left ventricular »eccentricity index«, as the reverse value of relative wall thickness, correlated well (r = 0.76) with the BMI values. The indices of left ventricular hypertrophy correlated with the BMI values slightly better in middle age groups than in the groups of the youngest or the eldest hypertensives. In conclusion, eccentric left ventricular hypertrophy does not seem to be a distinctive feature of hypertensive heart disease in obesity. There is only some tendency toward the »eccentricity« of left ventricular geometry which becomes more apparent in more severe forms of hypertension, especially in very obese persons

Statistical Estimation of Quantum Tomography Protocols Quality

A novel operational method for estimating the efficiency of quantum state tomography protocols is suggested. It is based on a-priori estimation of the quality of an arbitrary protocol by means of universal asymptotic fidelity distribution and condition number, which takes minimal value for better protocol. We prove the adequacy of the method both with numerical modeling and through the experimental realization of several practically important protocols of quantum state tomography

Improved implementation of nonclassicality test for a single particle

Recently a test of nonclassicality for a single qubit was proposed [R. Alicki and N. Van Ryn, J. Phys. A: Math. Theor. 41, 062001 (2008)]. We present an optimized experimental realization of this test leading to a 46 standard deviation violation of classicality. This factor of 5 improvement over our previous result was achieved by moving from the infrared to the visible where we can take advantage of higher efficiency and lower noise photon detectors.Comment: 4 pages, 1 figur