Synchronization of quantum communications over an optical classical communications channel.

Precise synchronization between a transmitter and receiver is crucial for quantum communications protocols such as quantum key distribution (QKD) to efficiently correlate the transmitted and received signals and increase the signal-to-noise ratio. In this work, we introduce a synchronization technique that exploits a co-propagating classical optical communications link and tests its performance in a free-space QKD system. Previously, existing techniques required additional laser beams or relied on the capability to retrieve the synchronization from the quantum signal itself; this approach, however, is not applicable in high channel loss scenarios. On the contrary, our method exploits classical and quantum signals locked to the same master clock, allowing the receiver to synchronize both the classical and quantum communications links by performing a clock-data-recovery routine on the classical signal. In this way, by exploiting the same classical communications already required for post-processing and key generation, no additional hardware is required, and the synchronization can be reconstructed from a high-power signal. Our approach is suitable for both satellite and fiber infrastructures, where a classical and quantum channel can be transmitted through the same link.

Tbit/s line-rate satellite feeder links enabled by coherent modulation and full-adaptive optics.

Free-space optical (FSO) communication technologies constitute a solution to cope with the bandwidth demand of future satellite-ground networks. They may overcome the RF bottleneck and attain data rates in the order of Tbit/s with only a handful of ground stations. Here, we demonstrate single-carrier Tbit/s line-rate transmission over a free-space channel of 53.42 km between the Jungfraujoch mountain top (3700 m) in the Swiss Alps and the Zimmerwald Observatory (895 m) near the city of Bern, achieving net-rates of up to 0.94 Tbit/s. With this scenario a satellite-ground feeder link is mimicked under turbulent conditions. Despite adverse conditions high throughput was achieved by employing a full adaptive optics system to correct the distorted wavefront of the channel and by using polarization-multiplexed high-order complex modulation formats. It was found that adaptive optics does not distort the reception of coherent modulation formats. Also, we introduce constellation modulation - a new four-dimensional BPSK (4D-BPSK) modulation format as a technique to transmit high data rates under lowest SNR. This way we show 53 km FSO transmission of 13.3 Gbit/s and 210 Gbit/s with as little as 4.3 and 7.8 photons per bit, respectively, at a bit-error ratio of 1 ∙ 10-3. The experiments show that advanced coherent modulation coding in combination with full adaptive optical filtering are proper means to make next-generation Tbit/s satellite communications practical.

Oral syphilis: a series of 5 cases.

Syphilis is an infectious, usually sexually transmitted, disease caused by Treponema pallidum, subspecies pallidum. Because of the increasing prevalence in Europe during the past few years, dentists could be confronted with patients with oral manifestations of syphilis. Because oral lesions are highly contagious, it is vital to make the correct diagnosis quickly to initiate the proper therapy and to interrupt the chain of infection. We present the cases of 5 patients with syphilis-related oral lesions. These cases are representative because of their clinical presentation, age, and gender distribution and the diagnostic approach. The aim of the present report is to emphasize the importance of the dentist knowing and identifying syphilis in different stages to diagnose the disease and institute treatment at an early stage.

Evaluation of location and dimensions of lingual foramina using limited cone-beam computed tomography.

PURPOSE: To assess retrospectively the frequency and location of mandibular lingual foramina and their bony canals with limited cone-beam computed tomography. PATIENTS AND METHODS: Of 389 consecutively taken cone-beam computed tomograms of the mandible, 191 fulfilled the inclusion criteria of adequate quality, dentate areas within the region of interest, and visualization of the mandibular inferior border. Foramina were located according to tooth areas and were grouped into midline, paramedian, and posterior foramina. Linear measurements included vertical and horizontal diameters of the foramen and its distance to the lower border of the mandible. In addition, the frequency of bony canals originating from lingual foramina was calculated, and the course and anastomoses with other anatomic structures were assessed. RESULTS: In total, 217 lingual foramina were detected in 1,054 sites. The midline of the symphysis had the highest frequency of foramina (96.2%), with the right first premolar area having the second highest frequency (27.5%). The mean diameter of lingual foramina ranged from 0.97 to 1.20 mm (horizontal diameter) and from 0.90 to 1.01 mm (vertical diameter). Sizes differed significantly between midline and posterior foramina. The mean distance from the foramen to the inferior mandibular border varied from 7.07 to 11.54 mm, with extreme outliers in all 3 groups. Overall, 95.4% of lingual foramina presented with a bony canal originating from the lingual surface, and 40.1% of these canals communicated with other anatomic structures, most frequently with the incisive canal. CONCLUSIONS: Mandibular lingual foramina and bony canals are frequently present and should be included in presurgical radiographic diagnostics.