Quantum Enhanced Balanced Heterodyne Readout for Differential Interferometry.

Conventional heterodyne readout schemes are now under reconsideration due to the realization of techniques to evade its inherent 3 dB signal-to-noise penalty. The application of high-frequency, quadrature-entangled, two-mode squeezed states can further improve the readout sensitivity of audio-band signals. In this Letter, we experimentally demonstrate quantum-enhanced heterodyne readout of two spatially distinct interferometers with direct optical signal combination, circumventing the 3 dB heterodyne signal-to-noise penalty. Applying a high-frequency, quadrature-entangled, two-mode squeezed state, we show further signal-to-noise improvement of an injected audio band signal of 3.5 dB. This technique is applicable for quantum-limited high-precision experiments, with application to searches for quantum gravity, searches for dark matter, gravitational wave detection, and wavelength-multiplexed quantum communication.

Reconstructing Gaussian bipartite states with a single polarization-sensitive homodyne detector.

We present a novel method to fully estimate Gaussian bipartite polarization states using only a single homodyne detector. Our approach is based on [Phys. Rev. Lett.102, 020502 (2009)10.1103/PhysRevLett.102.020502], but circumvents additional optics, and thereby losses, in the signal path. We provide an intuitive explanation of our scheme without needing to define auxiliary modes. With six independent measurements, we fully reconstruct the state's covariance matrix. We validate our method by comparing it to a conventional dual-homodyne measurement scheme.

Frequency-Dependent Squeezing from a Detuned Squeezer.

Frequency-dependent squeezing is a promising technique to overcome the standard quantum limit in optomechanical force measurements, e.g., gravitational wave detectors. For the first time, we show that frequency-dependent squeezing can be produced by detuning an optical parametric oscillator from resonance. Its frequency-dependent Wigner function is reconstructed quantum tomographically and exhibits a rotation by 39°, along which the noise is reduced by up to 5.5 dB. Our setup is suitable for realizing effective negative-mass oscillators required for coherent quantum noise cancellation.

High-precision cavity spectroscopy using high-frequency squeezed light.

In this article, we present a novel spectroscopy technique that improves the signal-to-shot-noise ratio without the need to increase the laser power. Detrimental effects by technical noise sources are avoided by frequency-modulation techniques (frequency up-shifting). Superimposing the signal on non-classical states of light leads to a reduced quantum noise floor. Our method reveals in a proof-of-concept experiment small signals at Hz to kHz frequencies even below the shot noise limit. Our theoretical calculations fully support our experimental findings. The proposed technique is interesting for applications such as high-precision cavity spectroscopy, e.g., for explosive trace gas detection where the specific gas might set an upper limit for the laser power employed.

Laser Power Stabilization beyond the Shot Noise Limit Using Squeezed Light.

High levels of laser power stability are necessary for high precision metrology applications. The classical limit for the achievable power stability is determined by the shot noise of the light used to generate a power control signal. Increasing the power of the detected light reduces the relative shot noise level and allows higher stabilities. However, sufficiently high power is not always available and the detection of high laser powers is challenging. Here, we demonstrate a nonclassical way to improve the achievable power stability without increasing the detected power. By the injection of a squeezed vacuum field of light we improve the classical laser power stability beyond its shot noise limit by 9.4_{-0.6}^{+0.6} dB at Fourier frequencies between 5 and 80 kHz. For only 90.6 µA of detected photocurrent we achieve a relative laser power noise of 2.0_{-0.1}^{+0.1}×10^{-8}/sqrt[Hz]. This is the first demonstration of a squeezed light-enhanced laser power stabilization and its performance is equivalent to an almost tenfold increase of detected laser power in a classical scheme. The analysis reveals that the technique presented here has the potential to achieve stability levels of 4.2×10^{-10}/sqrt[Hz] with 58 mA photocurrent measured on a single photodetector.

The discovery of the church of Rungholt, a landmark for the drowned medieval landscapes of the Wadden Sea World Heritage.

The UNESCO World Heritage Wadden Sea holds remains of a medieval cultural landscape shaped by interactions between man and natural forces. From the Netherlands to Denmark, human efforts of cultivating low-lying areas created a unique coastal landscape. Since the Middle Ages, storm floods widely drowned embanked cultural land and especially affected North Frisia (Germany), where once fertile marshland was permanently turned into tidal flats. One key region, the Edomsharde, was widely destroyed in 1362 AD. Medieval settlement remains still occur in the tidal flats around the island Hallig Südfall and are commonly associated with Edomsharde's trading centre Rungholt-ever since a symbol for the region's drowned landscapes and focus of this study. We present a first-time comprehensive reconstruction of this medieval settlement by means of new geophysical, geoarchaeological and archaeological data. Our results reveal remains of up to 64 newly found and rectified dwelling mounds, abundant drainage ditches, a seadike, and especially the discovery of Edomshardes's main church as important landmark in this former cultural landscape. These finds together with the documented imported goods confirm a thriving society, involved in transregional trade and thereby close a significant gap in medieval history not only for North Frisia, but the entire Wadden Sea region.

Lost in the North Sea-Geophysical and geoarchaeological prospection of the Rungholt medieval dyke system (North Frisia, Germany).

We performed geophysical and geoarchaeological investigations in the Wadden Sea off North Frisia (Schleswig-Holstein, Germany) to map the remains and to determine the state of preservation of the medieval settlement of Rungholt, especially its southern dyke segment, called the Niedam dyke. Based on archaeological finds and historical maps, Rungholt is assumed to be located in the wadden sea area around the island Hallig Südfall. During medieval and early modern times, extreme storm events caused major land losses, turning cultivated marshland into tidal flats. Especially the 1st Grote Mandrenke (or St. Marcellus' flood), an extreme storm surge event in 1362 AD, is addressed as the major event that flooded and destroyed most of the Rungholt cultural landscape. Cultural traces like remains of dykes, drainage ditches, tidal gates, dwelling mounds or even plough marks were randomly surveyed and mapped in the tidal flats by several authors at the beginning of the 20th century. Due to the tidal flat dynamics with frequently shifting tidal creeks and sand bars, the distribution of cultural remains visible at the surface is rapidly changing, making it hard to create a comprehensive map of the cultural landscape by surveying. Today, the Niedam dyke area is fully covered by tidal flat sediments, depriving any remains from further archaeological investigation. Since little is known about the precise location or state of preservation of these remains, our investigation aimed at the rediscovery of the medieval dyke system and associated structure with modern and accurate geophysical, geodetical and geoarchaeological methods. Magnetic gradiometry revealed a large part of the medieval dyke, confirming two tidal gates and several terps connected inland with the dyke, providing a detailed example of a Frisian medieval dyke system. Based on our results, the so far inaccurate and incomplete maps of this part of Rungholt can now be specified and completed. Beyond that, seismic reflection profiles give a first depth resolving insight in the remains of the dyke system, revealing a severe threat to the medieval remains by erosion. The site is exemplary for the entire North Frisian coast, that was influenced by multiple flood events in the middle ages to modern times.

What are the benefits of medical screening and surveillance?

Pre-employment examination is considered to be an important practice and is commonly performed in several countries within the European Union. The benefits of medical surveillance programmes are not generally accepted and their structure is often inconsistent. The aim of this review was to evaluate, on the basis of the available literature, the usefulness of medical screening and surveillance. MEDLINE was searched from its inception up to March 2010. Retrieved literature was evaluated in a peer-review process and relevant data was collected following a systematic extraction schema. Pre-placement screening identifies subjects who are at an increased risk for developing work-related allergic disease, but pre-employment screening is too low to be used as exclusion criteria. Medical surveillance programmes can identify workers who have, or who are developing, work-related asthma. These programmes can also be used to avoid worsening of symptoms by implementing preventive measures. A combination of different tools within the surveillance programme, adjusted for the risk of the individual worker, improves the predictive value. Medical surveillance programmes provide medical as well as socioeconomic benefits. However, pre-employment screening cannot be used to exclude workers. They may act as a starting point for surveillance strategies. A stratified approach can increase the effectiveness and reduce the costs for such programmes.

The management of work-related asthma guidelines: a broader perspective.

The aim of the European Respiratory Society work-related asthma guidelines is to present the management and prevention options of work-related asthma and their effectiveness. Work-related asthma accounts for 5-25% of all adult asthma cases and is responsible for a significant socioeconomic burden. Several hundred occupational agents, mainly allergens but also irritants and substances with unknown pathological mechanisms, have been identified as causing work-related asthma. The essential message of these guidelines is that the management of work-related asthma can be considerably optimised based on the present knowledge of causes, risk factors, pathomechanisms, and realistic and effective interventions. To reach this goal we urgently require greatly intensified primary preventive measures and improved case management. There is now a substantial body of evidence supporting the implementation of comprehensive medical surveillance programmes for workers at risk. Those workers who fail surveillance programmes need to be referred to a clinician who can confirm or exclude an occupational cause. Once work-related asthma is confirmed, a revised risk assessment in the workplace is needed to prevent further cases. These new guidelines confirm and extend already existing statements and recommendations. We hope that these guidelines will initiate the much-needed research that is required to fill the gaps in our knowledge and to initiate substantial improvements in preventative measures.

Lung function in asbestos-exposed workers, a systematic review and meta-analysis.

BACKGROUND: A continuing controversy exists about whether, asbestos exposure is associated with significant lung function impairments when major radiological abnormalities are lacking. We conducted a systematic review and meta-analysis in order to assess whether asbestos exposure is related to impairment of lung function parameters independently of the radiological findings. METHODS: MEDLINE was searched from its inception up to April 2010. We included studies that assessed lung function parameters in asbestos exposed workers and stratified subjects according to radiological findings. Estimates of VC, FEV1 and FEV1/VC with their dispersion measures were extracted and pooled. RESULTS: Our meta-analysis with data from 9,921 workers exposed to asbestos demonstrates a statistically significant reduction in VC, FEV1 and FEV1/VC, even in those workers without radiological changes. Less severe lung function impairments are detected if the diagnoses are based on (high resolution) computed tomography rather than the less sensitive X-ray images. The degree of lung function impairment was partly related to the proportion of smokers included in the studies. CONCLUSIONS: Asbestos exposure is related to restrictive and obstructive lung function impairment. Even in the absence of radiological evidence of parenchymal or pleural diseases there is a trend for functional impairment.