[Outcome Quality of Open General Psychiatric Inpatient Treatment at the Meso Level - an Observational Study in an Urban German General Hospital]. / Zur Ergebnisqualität der allgemeinpsychiatrischen offenstationären Krankenhausbehandlung auf der Mesoebene - eine prospektive Studie aus einem urbanen Allgemeinkrankenhaus.

BACKGROUND: Inpatient treatment (meso level) in psychiatric hospitals is commonly assumed to be effective. However, there is very little evidence-based data on this issue. OBJECTIVES AND METHODS: First evaluation of the outcome quality of an inpatient general psychiatric treatment in a German general hospital using multifaceted quality indicators (symptom severity, wellbeing, self-efficacy, depressive avoidance, patients' satisfaction with the treatment) was carried out. Patients with a wide range of psychiatric diagnoses (ICD-10 F2-F6) were randomly assigned to this naturalistic single-group pre-post study. For ethical and methodological reasons, only adult inpatients treated in open general psychiatric wards were enrolled. RESULTS: The sample (n = 110, 58.2 % females) had a mean age of 47.2 (SD 15.9) years. 67 (60.9 %) and 29 (26.4 %) patients had at least one or two additional psychiatric diagnoses, respectively. 84 (76.4 %) and 62 (56.4 %) patients had a minimum of one or two additional somatic diagnoses, respectively. The treatment lasted 38 (SD 36; median 28.5) days. Significant positive treatment effects for all quality indicators were found at regular hospital discharge. The effect sizes varied between Cohen's d = 0.17 - 0.62 ("intention-to-treat" population, n = 110) and d = 0.28 - 0.99 ("completer" population, n = 70). DISCUSSION AND CONCLUSION: This study provides direct evidence for the effectiveness of an open inpatient general psychiatric hospital treatment at the meso level. The results, however, are not representative for all German general psychiatric wards because of major differences between hospitals in personnel resources and framework conditions.

Nonlinear interaction between single photons.

Harnessing nonlinearities strong enough to allow single photons to interact with one another is not only a fascinating challenge but also central to numerous advanced applications in quantum information science. Here we report the nonlinear interaction between two single photons. Each photon is generated in independent parametric down-conversion sources. They are subsequently combined in a nonlinear waveguide where they are converted into a single photon of higher energy by the process of sum-frequency generation. Our approach results in the direct generation of photon triplets. More generally, it highlights the potential for quantum nonlinear optics with integrated devices and, as the photons are at telecom wavelengths, it opens the way towards novel applications in quantum communication such as device-independent quantum key distribution.

Interaction of independent single photons based on integrated nonlinear optics.

The parametric interaction of light beams in nonlinear materials is usually thought to be too weak to be observed when the fields involved are at the single-photon level. However, such single-photon level nonlinearity is not only fundamentally fascinating but holds great potential for emerging technologies and applications involving heralding entanglement at a distance. Here we use a high-efficiency waveguide to demonstrate the sum-frequency generation between a single photon and a single-photon level coherent state. The use of an integrated, solid state, room temperature device and telecom wavelengths makes this type of system directly applicable to future quantum communication technologies such as device-independent quantum key distribution.

Widely tunable midinfrared difference frequency generation in orientation-patterned GaAs pumped with a femtosecond Tm-fiber system.

We demonstrate a midinfrared source tunable from 6.7 to 12.7 µm via difference frequency generation (DFG) in orientation-patterned GaAs, with 1.3 mW average output power. The input pulses are generated via Raman self-frequency shift of a femtosecond Tm-doped-fiber laser system in a fluoride fiber. We numerically model the DFG process and show good agreement between simulations and experiments. We use this numerical model to show an improved design using longer pump pulses.

Long-wavelength-pumped upconversion single-photon detector at 1550 nm: performance and noise analysis.

We demonstrate upconversion-assisted single-photon detection for the 1.55-µm telecommunications band based on a periodically poled lithium niobate (PPLN) waveguide pumped by a monolithic PPLN optical parametric oscillator. We achieve an internal conversion efficiency of 86%, which results in an overall system detection efficiency of 37%, with excess noise as low as 10(3) counts s(-1). We measure the dark count rate versus the upconversion pump-signal frequency separation and find the results to be consistent with noise photon generation by spontaneous anti-Stokes Raman scattering. These results enable detailed design guidelines for the development of low-noise quantum frequency conversion systems, which will be an important component of fiber-optic quantum networks.

Efficiency pedestal in quasi-phase-matching devices with random duty-cycle errors.

It is shown that random duty-cycle errors in quasi-phase-matching (QPM) nonlinear optical devices enhance the efficiency of processes far from the QPM peak. An analytical theory is shown to agree well with numerical solutions of second-harmonic generation (SHG) in disordered QPM gratings. The measured efficiency of 1550 nm band SHG in a periodically poled lithium niobate (PPLN) waveguide away from the QPM peak agrees with observations of domain disorder in a PPLN wafer by Zygo interferometry. If suppression of parasitic nonlinear interactions is important in a specific application of QPM devices, control of random duty-cycle errors is critical.

Influence of domain disorder on parametric noise in quasi-phase-matched quantum frequency converters.

Ideal quantum frequency conversion (QFC) devices enable wavelength translation of a quantum state of light while preserving its essential quantum characteristics, namely photon statistics and coherence. However, the generation of noise photons due to spontaneous scattering of the strong classical pump used in the three-wave mixing process can limit QFC fidelity. We experimentally and theoretically characterize the noise properties of a difference-frequency generation device for QFC and find that fabrication errors in the quasi-phase-matching grating enhance generation of noise photons by parametric fluorescence.

All-optical wavelength conversion of a 100-Gb/s polarization-multiplexed signal.

We present the results of an in-depth experimental investigation about all-optical wavelength conversion of a 100-Gb/s polarization-multiplexed (POLMUX) signal. Each polarization channel is modulated at 25 Gbaud by differential quadrature phase-shift keying (DQPSK). The conversion is realized exploiting the high nonlinear chi((2)) coefficient of a periodically poled lithium niobate waveguide, in a polarization-independent configuration. We find that slight non-idealities in the polarization independent setup of the wavelength converter can significantly impair the performance of POLMUX systems. We show that high-quality wavelength conversion can be nevertheless achieved for both the polarization channels, provided that an accurate optimization of the setup is performed. This is the first demonstration, to the best of our knowledge, of the possibility to obtain penalty-free all-optical wavelength conversion in a 100-Gb/s POLMUX transmission system using direct-detection.

Fiber-laser frequency combs with subhertz relative linewidths.

We investigate the comb linewidths of self-referenced, fiber-laser-based frequency combs by measuring the heterodyne beat signal between two independent frequency combs that are phase locked to a common cw optical reference. We demonstrate that the optical comb lines can exhibit instrument-limited, subhertz relative linewidths across the comb spectra from 1200 to 1720 nm with a residual integrated optical phase jitter of approximately 1 rad in a 60 mHz to 500 kHz bandwidth. The projected relative pulse timing jitter is approximately 1 fs. This performance approaches that of Ti:sapphire frequency combs.

Integrated self-referenced frequency-comb laser based on a combination of fiber and waveguide technology.

An optically integrated self-referenced frequency comb laser is demonstrated. The system consists of a passively-modelocked Er-fiber laser, a butt-coupled periodically poled lithium niobate (PPLN) waveguide phase-sensor and an electronic feedback loop for carrier-envelope-offset (CEO) phase stabilization. The fceo-beat-signal has a linewidth of 62 kHz and is detected with a S/N-ratio of 40 dB, with greatly reduced pulse energy requirements compared to bulk crystal phase-sensors. To our knowledge this is the first self-referenced frequency-comb system entirely based on guided-wave technology.