Maximum likelihood estimation of photon number distribution from homodyne statistics

We present a method for reconstructing the photon number distribution from the homodyne statistics based on maximization of the likelihood function derived from the exact statistical description of a homodyne experiment. This method incorporates in a natural way the physical constraints on the reconstructed quantities, and the compensation for the nonunit detection efficiency.Comment: 3 pages REVTeX. Final version, to appear in Phys. Rev. A as a Brief Repor

Quantum engineering of squeezed states for quantum communication and metrology

We report the experimental realization of squeezed quantum states of light, tailored for new applications in quantum communication and metrology. Squeezed states in a broad Fourier frequency band down to 1 Hz has been observed for the first time. Nonclassical properties of light in such a low frequency band is required for high efficiency quantum information storage in electromagnetically induced transparency (EIT) media. The states observed also cover the frequency band of ultra-high precision laser interferometers for gravitational wave detection and can be used to reach the regime of quantum non-demolition interferometry. And furthermore, they cover the frequencies of motions of heavily macroscopic objects and might therefore support the attempts to observe entanglement in our macroscopic world.Comment: 12 pages, 3 figure

Broadband detection of squeezed vacuum: A spectrum of quantum states

We demonstrate the simultaneous quantum state reconstruction of the spectral modes of the light field emitted by a continuous wave degenerate optical parametric amplifier. The scheme is based on broadband measurement of the quantum fluctuations of the electric field quadratures and subsequent Fourier decomposition into spectral intervals. Applying the standard reconstruction algorithms to each bandwidth-limited quantum trajectory, a "spectrum" of density matrices and Wigner functions is obtained. The recorded states show a smooth transition from the squeezed vacuum to a vacuum state. In the time domain we evaluated the first order correlation function of the squeezed output field, showing good agreement with the theory.Comment: 11 pages, 5 figure

Magnetoelectric and HR-STEM investigations on eutectic CoFe₂O₄-Ba_1-xSr_xTiO₃ composites

Multiferroic Ba1–xSrxTiO3–CoFe2O4 (x = 0.03, 0.05) composites with rarely investigated 3-3 connectivity were prepared by eutectic crystallization in an optical floating zone furnace. High-resolution scanning transmission electron microscopy investigations of the CoFe2O4–BaTiO3 interface revealed an almost perfect connection between both components. These micrographs also showed that the impact of post-annealing in air was much larger than expected and resulted in formation of small BaTiO3 inclusions in the CoFe2O4 phase. The magnetoelectric coefficient αME was studied in detail with respect to its dependence on the static magnetic field, the frequency of the driving AC-field and temperature. Furthermore, the influence of different growth rates (5, 10 and 20 mm h-1), chemical composition, sample thickness and the alignment of electrical polarization and magnetic field (collinear or vertical) on the magnetoelectric properties were studied. The largest value of αME = 1.3 mV Oe-1 cm-1 was found for a sample grown at 5 mm h-1. For even slower growth rates, a higher Sr content was required to avoid the formation of impurity phases leading to a decrease of αME

Optimal Alignment Sensing of a Readout Mode Cleaner Cavity

Critically coupled resonant optical cavities are often used as mode cleaners in optical systems to improve the signal to noise ratio (SNR) of a signal that is encoded as an amplitude modulation of a laser beam. Achieving the best SNR requires maintaining the alignment of the mode cleaner relative to the laser beam on which the signal is encoded. An automatic alignment system which is primarily sensitive to the carrier field component of the beam will not, in general, provide optimal SNR. We present an approach that modifies traditional dither alignment sensing by applying a large amplitude modulation on the signal field, thereby producing error signals that are sensitive to the signal sideband field alignment. When used in conjunction with alignment actuators, this approach can improve the detected SNR; we demonstrate a factor of 3 improvement in the SNR of a kilometer-scale detector of the Laser Interferometer Gravitational-wave Observatory. This approach can be generalized to other types of alignment sensors

Nitrous oxide in the North Atlantic Ocean

In order to get a comprehensive picture of the distribution of nitrous oxide (N2O) in the North Atlantic Ocean, measurements of dissolved nitrous oxide were made during three cruises in the tropical, subtropical and cold-temperate North Atlantic Ocean in October/November 2002, March/April 2004, and May 2002, respectively. To account for the history of atmospheric N2O, we suggest a new depth-dependent calculation of excess N2O (ΔN2O). N2O depth profiles showed supersaturation throughout the water column with a distinct increasing trend from the cold-temperate to the tropical region. Lowest nitrous oxide concentrations, near equilibrium and with an average of 11.0±1.7 nmol L−1, were found in the cold-temperate North Atlantic where the profiles showed no clear maxima. Highest values up to 37.3 nmol L−1 occurred in the tropical North Atlantic with clear maxima at approximately 400 m. A positive correlation of nitrous oxide with nitrate, as well as excess nitrous oxide with the apparent oxygen utilization (AOU), was only observed in the subtropical and tropical regions. Therefore, we conclude that the formation of nitrous oxide via nitrification occurs in the tropical region rather than in the cold-temperate region of the North Atlantic Ocea

Distribution of N₂O in the Baltic Sea during transition from anoxic to oxic conditions

In January 2003, a major inflow of cold and oxygen-rich North Sea Water terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow in the production of nitrous oxide (N2O), we measured dissolved and atmospheric N<2O at 26 stations in the southern and central Baltic Sea in October 2003. At the time of our cruise, water renewal had proceeded to the eastern Gotland Basin, whereas the western Gotland Basin was still unaffected by the inflow. The deep water renewal was detectable in the distributions of temperature, salinity, and oxygen concentrations as well as in the distribution of the N2O concentrations: Shallow stations in the Kiel Bight and Pomeranian Bight were well-ventilated with uniform N2O concentrations near equilibrium throughout the water column. In contrast, stations in the deep basins, such as the Bornholm and the Gotland Deep, showed a clear stratification with deep water affected by North Sea Water. Inflowing North Sea Water led to changed environmental conditions, especially enhanced oxygen (O2) or declining hydrogen sulphide (H2S) concentrations, thus, affecting the conditions for the production of N2O. Pattern of N2O profiles and correlations with parameters like oxygen and nitrate differed between the basins. Because of the positive correlation between ΔN2O and AOU in oxic waters the dominant production pathway seems to be nitrification rather than denitrification. Advection of N2O by North Sea Water was found to be of minor importance. A rough budget revealed a significant surplus of in situ produced N2O after the inflow. However, due to the permanent halocline, it can be assumed that the N2O produced does not reach the atmosphere. Hydrographic aspects therefore are decisive factors determining the final release of N2O produced to the atmosphere

Open Repair Versus Thoracic Endovascular Aortic Repair in Multiple-Injured Patients: Observations From a Level-1 Trauma Center

Background: Blunt trauma of the thoracic aorta is a rare but potentially life-threatening entity. Intimal tears are a domain of non-operative management, whereas all other types of lesions should be repaired urgently. There is now a clear trend favoring minimally invasive stent grafting over open surgical repair. Objectives: The aim of the present study was to retrospectively evaluate the mortality and morbidity with either treatment option. Therefore, a retrospective observational study was performed to compare two different treatment methods at two different time periods at one trauma center. Patients and Methods: Between 1977 and 2012, all severely injured patients referred to our level 1 trauma center were screened for blunt aortic injuries. We compared baseline characteristics, 30-day and overall mortality, morbidity, duration of intensive care treatment, procedure time, and transfusion of packed red blood between patients who underwent open surgical or stent repair. Results: During the observation period, 45 blunt aortic injuries were recorded. The average Injury Severity Score (ISS) was 41.8 (range 29 - 68). Twenty-five patients underwent Open Repair (OR), and another 20 patients were scheduled to emergency stent grafting. The 30-day mortality in the surgical and stent groups were 5/25 (20%) and 2/20 (10%), respectively. The average time for open surgery was 151 minutes; the mean time for stent grafting was 67 minutes (P = 0.001). Postoperative stay on the intensive care unit was between one and 59 days (median 10) in group one and between four and 50 days in group two (median 26)(P = 0.03). Patients undergoing OR required transfusion of 6.0 units of packed red cells in median; patients undergoing stent grafting required a median of 2.0 units of packed red cells (P < 0.001). In the stent grafting group, 30-day mortality was 10% (2/20). Conclusions: Due to more sophisticated diagnostic tools and surgical approaches, mortality and morbidity of blunt aortic injuries were significantly reduced over the years compared to thoracic endovascular aortic repair and OR over two different time periods

Nitrous oxide water column distribution during the transition from anoxic to oxic conditions in the Baltic Sea

International audienceIn January 2003, a major inflow of cold and oxygen-rich North Sea Water in the Baltic Sea terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow to the Baltic Sea with regard to the production of nitrous oxide (N2O), we measured dissolved and atmospheric N2O at 26 stations in the southern and central Baltic Sea in October 2003. At the time of our cruise, water renewal had proceeded to the eastern Gotland Basin, whereas the western Gotland Basin was still unaffected by the inflow. The deep water renewal was detectable in the distributions of temperature, salinity, and oxygen concentrations as well as in the distribution of the N2O concentrations: Shallow stations in the Kiel Bight and Pomeranian Bight were well-ventilated with uniform N2O concentrations near equilibrium throughout the water column. In contrast, stations in the deep basins, such as the Bornholm and the Gotland Deep, showed a clear stratification with deep water affected by North Sea Water. Inflowing North Sea Water led to changed environmental conditions, especially enhanced oxygen (O2) or declining hydrogen sulfide (H2S) concentrations, thus, affecting the conditions for the production of N2O. Pattern of N2O profiles and correlations with parameters like oxygen and nitrate differed between the basins. The dominant production pathway seems to be nitrification rather than denitrification. No indications for advection of N2O by North Sea Water were found. A rough budget revealed a significant surplus of in situ produced N2O after the inflow. However, due to the permanent halocline, it can be assumed that the formed N2O does not reach the atmosphere. Hydrographic aspects therefore are decisive factors determining the final release of produced N2O to the atmosphere