4,063 research outputs found
Avoiding The Ask: A Field Experiment on Altruism, Empathy, and Charitable Giving
What triggers giving? We explore this in a randomized natural field experiment during the Salvation Army's annual campaign. Solicitors were at one or both of two main entrances to a supermarket, making the solicitation either easy or difficult to avoid. Additionally, solicitors were either silent, or asked "please give" to passersby. We observed over 17,000 passings over four days, and found dramatic avoidance of the solicitors, but only during a direct ask. Furthermore, asking increased donations 75%. Across all conditions, seeking the solicitor was exceedingly rare. The results do not support static views of altruism, such as inequity aversion, and instead highlight the importance of social cues and psychological features of the giver-receiver interaction. We argue that avoidance could evidence a lack of altruism or self-control strategy to deal with empathic reflexes to give.
Reliable source of conditional non-Gaussian states from single-mode thermal fields
We address both theoretically and experimentally the generation of pulsed
non-Gaussian states from classical Gaussian ones by means of conditional
measurements. The setup relies on a beam splitter and a pair of linear
photodetectors able to resolve up to tens of photons in the two outputs. We
show the reliability of the setup and the good agreement with the theory for a
single-mode thermal field entering the beam splitter and present a thorough
characterization of the photon statistics of the conditional states.Comment: 18 pages, 12 figure
Experimental reconstruction of photon statistics without photon counting
Experimental reconstructions of photon number distributions of both
continuous-wave and pulsed light beams are reported. Our scheme is based on
on/off avalanche photodetection assisted by maximum-likelihood estimation and
does not involve photon counting. Reconstructions of the distribution for both
semiclassical and quantum states of light are reported for single-mode as well
as for multimode beams.Comment: Revised version: in press on PRL. 4 pages, 4 fig
Conditional measurements on multimode pairwise entangled states from spontaneous parametric downconversion
We address the intrinsic multimode nature of the quantum state of light
obtained by pulsed spontaneous parametric downconversion and develop a
theoretical model based only on experimentally accessible quantities. We
exploit the pairwise entanglement as a resource for conditional multimode
measurements and derive closed formulas for the detection probability and the
density matrix of the conditional states. We present a set of experiments
performed to validate our model in different conditions that are in excellent
agreement with experimental data. Finally, we evaluate nonGaussianity of the
conditional states obtained from our source with the aim of discussing the
effects of the different experimental parameters on the efficacy of this type
of conditional state preparation
Self-consistent characterization of light statistics
We demonstrate the possibility of a self-consistent characterization of the
photon-number statistics of a light field by using photoemissive detectors with
internal gain simply endowed with linear input/output responses. The method can
be applied to both microscopic and mesoscopic photon-number regimes. The
detectors must operate in the linear range without need of photon-counting
capabilities.Comment: To be published in "Journal of Modern Optics
State reconstruction by on/off measurements
We demonstrate a state reconstruction technique which provides either the
Wigner function or the density matrix of a field mode and requires only
avalanche photodetectors, without any phase or amplitude discrimination power.
It represents an alternative, of simpler implementation, to quantum homodyne
tomography.Comment: 6 pages, 4 figures, revised and enlarged versio
Follow Up of GW170817 and Its Electromagnetic Counterpart by Australian-Led Observing Programmes
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor
Parallel spatial intensity correlations to decode random frequency-downconverted images
We record frequency-downconverted images that are chaotic, as they are obtained in a chi((2)) crystal from the interaction of two pulsed pseudo-thermal fields of which the one at the higher frequency encountered the imaged object. Spatial correlations of the intensity fluctuations in these chaotic images with the intensity of a single spatial Fourier component of the low-frequency input field, allow image retrieval if the number of records on which the ensemble-averages are calculated is suitably large. When it is too small to achieve a satisfactory result, we show that computing the correlations in parallel with different components of the low-frequency input field, shifting the correlation maps according to a rule suggested by 3D phase-matching, and averaging them, leads to the recovery of the downconverted image. The method can be used for secure and fast image transmission
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