Generation of pulsed bipartite entanglement using four-wave mixing

Using four-wave mixing in a hot atomic vapor, we generate a pair of entangled twin beams in the microsecond pulsed regime near the D1 line of $^{85}$Rb, making it compatible with commonly used quantum memory techniques. The beams are generated in the bright and vacuum-squeezed regimes, requiring two separate methods of analysis, without and with local oscillators, respectively. We report a noise reduction of up to $3.8\pm 0.2$ dB below the standard quantum limit in the pulsed regime and a level of entanglement that violates an Einstein--Podolsky--Rosen inequality.Comment: 10 pages, 5 figures, accepted for publication in New Journal Of Physici

Comprehensive flood mitigation and management in the Chi River Basin, Thailand

Severe flooding of the flat downstream area of the Chi River Basin occurs frequently. This flooding is causing catastrophic loss of human lives, damage and economic loss. Effective flood management requires a broad and practical approach. Although flood disasters cannot completely be prevented, major part of potential loss of lives and damages can be reduced by comprehensive mitigation measures. In this paper, the effects of river normalisation, reservoir operation, green river (bypass), and retention have been analysed by using integrated hydrologic and hydraulic modelling. Every tributary has been simulated by a process-based hydrological model (SWAT) coupled with the 1D/2D SOBEK river routing model. Model simulation results under the design rainfall event, i.e. flood depth, flood extent, and damages for the situation with and without flood mitigation measures have been compared and evaluated to determine an optimal set of mitigation measures. The results reveal that a combination of river normalisation, reservoir operation, and green river (bypass) is most effective as it can decrease the extent of the 100-year flood event by approximately 24% and 31% for the economic damage. The results of this study will be useful for improving the present flood defence practice in the Chi River Basi

Imaging using quantum noise properties of light

We show that it is possible to estimate the shape of an object by measuring only the fluctuations of a probing field, allowing us to expose the object to a minimal light intensity. This scheme, based on noise measurements through homodyne detection, is useful in the regime where the number of photons is low enough that direct detection with a photodiode is difficult but high enough such that photon counting is not an option. We generate a few-photon state of multi-spatial-mode vacuum-squeezed twin beams using four-wave mixing and direct one of these twin fields through a binary intensity mask whose shape is to be imaged. Exploiting either the classical fluctuations in a single beam or quantum correlations between the twin beams, we demonstrate that under some conditions quantum correlations can provide an enhancement in sensitivity when estimating the shape of the object