Strong Einstein-Podolsky-Rosen entanglement from a single squeezed light source

Einstein-Podolsky-Rosen (EPR) entanglement is a criterion that is more demanding than just certifying entanglement. We theoretically and experimentally analyze the low resource generation of bi-partite continuous variable entanglement, as realized by mixing a squeezed mode with a vacuum mode at a balanced beam splitter, i.e. the generation of so-called vacuum-class entanglement. We find that in order to observe EPR entanglement the total optical loss must be smaller than 33.3 %. However, arbitrary strong EPR entanglement is generally possible with this scheme. We realize continuous wave squeezed light at 1550 nm with up to 9.9 dB of non-classical noise reduction, which is the highest value at a telecom wavelength so far. Using two phase controlled balanced homodyne detectors we observe an EPR co-variance product of 0.502 \pm 0.006 < 1, where 1 is the critical value. We discuss the feasibility of strong Gaussian entanglement and its application for quantum key distribution in a short-distance fiber network.Comment: 4 pages, 4 figure

Supercontinuum pulse shaping in the few-cycle regime

The synthesis of nearly arbitrary supercontinuum pulse forms is demonstrated with sub-pulse structures that maintain a temporal resolution in the few-cycle regime. Spectral broadening of the 35 fs input pulses to supercontinuum bandwidths is attained in a controlled two-stage sequential filamentation in air at atmospheric pressure, facilitating a homogeneous power density over the full spectral envelope in the visible to near infrared spectral range. Only standard optics and a liquid crystal spatial light modulator (LC-SLM) are employed for achieving pulse compression to the sub 5 fs regime with pulse energies of up to 60 μJ and a peak power of 12 GW. This constitutes the starting point for further pulse form synthesis via phase modulation within the sampling limit of the pulse shaper. Transient grating frequency-resolved optical gating (TG-FROG) allows for the characterization of pulse forms that extend over several hundred femtoseconds with few-cycle substructure

Implementation of Quantum Key Distribution with Composable Security Against Coherent Attacks using Einstein-Podolsky-Rosen Entanglement

Secret communication over public channels is one of the central pillars of a modern information society. Using quantum key distribution (QKD) this is achieved without relying on the hardness of mathematical problems which might be compromised by improved algorithms or by future quantum computers. State-of-the-art QKD requires composable security against coherent attacks for a finite number of samples. Here, we present the first implementation of QKD satisfying this requirement and additionally achieving security which is independent of any possible flaws in the implementation of the receiver. By distributing strongly Einstein-Podolsky-Rosen entangled continuous variable (CV) light in a table-top arrangement, we generated secret keys using a highly efficient error reconciliation algorithm. Since CV encoding is compatible with conventional optical communication technology, we consider our work to be a major promotion for commercialized QKD providing composable security against the most general channel attacks.Comment: 7 pages, 3 figure

Endoscopically assisted nerve decompression of rare nerve compression syndromes at the upper extremity

Background: Besides carpal tunnel and cubital tunnel syndrome, other nerve compression or constriction syndromes exist at the upper extremity. This study was performed to evaluate and summarize our initial experience with endoscopically assisted decompression. Materials and methods: Between January 2011 and March 2012, six patients were endoscopically operated for rare compression or hour-glass-like constriction syndrome. This included eight decompressions: four proximal radial nerve decompressions, and two combined proximal median nerve and anterior interosseus nerve decompressions. Surgical technique and functional outcomes are presented. Results: There were no intraoperative complications in the series. Endoscopy allowed both identifying and removing all the compressive structures. In one case, the proximal radial neuropathy developed for 10years without therapy and a massive hour-glass nerve constriction was observed intraoperatively which led us to perform a concurrent complementary tendon transfer to improve fingers and thumb extension. Excellent results were achieved according to the modified Roles and Maudsley classification in five out of six cases. All but one patient considered the results excellent. The poorest responder developed a CRPS II and refused post-operative physiotherapy. Conclusion: Endoscopically assisted decompression in rare compression syndrome of the upper extremity is highly appreciated by patients and provides excellent functional results. This minimally invasive surgical technique will likely be further described in future clinical studie

Kyphoplasty for treatment of osteoporotic vertebral fractures: a prospective non-randomized study

Background: Minimally invasive augmentation techniques of vertebral bodies have been advocated to treat osteoporotic vertebral body compression fractures (VBCFs). Kyphoplasty is designed to address both fracture-related pain as well as kyphotic deformity usually associated with fracture. Previous studies have indicated the potential of this technique for reduction of vertebral body height, but there has been little investigation into whether this has a lasting effect. The current study reports on our experience and the one-year results in 27 kyphoplasty procedures (24 patients) for osteoporotic VBCFs. Results: All but one patient experienced pain relief following the procedure (on VAS 1-10)—with a lasting effect over the follow-up period in 25 cases. An average vertebral kyphosis reduction of 47.7% was achieved with no loss of reduction after one year. The potential for reduction was statistically related to the pre-operative amount of kyphosis, the level treated, and the age of the fracture, but not to the age of the patient. During follow-up, one fracture adjacent to a treated level was observed. Pain relief was not related to the amount of reduction. Conclusion: Kyphoplasty is an effective treatment of VBCFs in terms of pain relief and durable reduction of deformity. Whether spinal realignment results in an improved long-term clinical outcome remains to be investigate

Continuous Variable Quantum Key Distribution: Finite-Key Analysis of Composable Security against Coherent Attacks

We provide a security analysis for continuous variable quantum key distribution protocols based on the transmission of squeezed vacuum states measured via homodyne detection. We employ a version of the entropic uncertainty relation for smooth entropies to give a lower bound on the number of secret bits which can be extracted from a finite number of runs of the protocol. This bound is valid under general coherent attacks, and gives rise to keys which are composably secure. For comparison, we also give a lower bound valid under the assumption of collective attacks. For both scenarios, we find positive key rates using experimental parameters reachable today.Comment: v2: new author, technical inaccuracy corrected, new plots, v3: substantially improved key rates against coherent attacks (due to correction of an error in the numerical computation

Macroreplantations of the upper extremity: a series of 11 patients

Introduction: Micro- or macroreplantation is classified depending on the level of amputation, distal or proximal to the wrist. This study was performed to review our experience in macroreplantation of the upper extremity with special attention to technical considerations and outcomes. Materials and methods: Between January 1990 and December 2010, 11 patients with a complete amputation of the upper extremity proximal to the wrist were referred for replantations to our department. The patients, one woman and ten men, had a mean age of 43.4±18.2years (range 19-76years). There were two elbow, two proximal forearm, four mid-forearm, and three distal forearm amputations. The mechanism of injury was crush in four, crush-avulsion in five and guillotine amputation in two patients. The Chen classification was used to assess the postoperative outcomes. The mean follow-up after macroreplantation was 7.5±6.3years (range 2-21years). Results: All but one were successfully replanted and regained limb function: Chen I in four cases (36%), Chen II in three cases (27%), Chen III in two cases (18%), and Chen IV in one patient (9%). We discuss the steps of the macroreplantation technique, the need to minimize ischemic time and the risk of ischemia reperfusion injuries. Conclusion: Thanks to improvements in technique, the indications for limb preservation after amputation can be expanded. However, because of their rarity, replantations should be performed at specialist replantation centers. Level of evidence: Level I

Gaussian entanglement for quantum key distribution from a single-mode squeezing source

We report the suitability of an Einstein-Podolsky-Rosen entanglement source for Gaussian continuous-variable quantum key distribution at 1550 nm. Our source is based on a single continuous-wave squeezed vacuum mode combined with a vacuum mode at a balanced beam splitter. Extending a recent security proof, we characterize the source by quantifying the extractable length of a composable secure key from a finite number of samples under the assumption of collective attacks. We show that distances in the order of 10 km are achievable with this source for a reasonable sample size despite the fact that the entanglement was generated including a vacuum mode. Our security analysis applies to all states having an asymmetry in the field quadrature variances, including those generated by superposition of two squeezed modes with different squeezing strengths.EU/FP7/Q-ESSENCEHALOSTARDFG/WE-1240/12-1BMBF/QUOREPJapan Society for the Promotion of Science/KAKENHI/24-02793EU/FP7/COQUI

Infrared Photodissociation Spectroscopy of C2n+1N− Anions with n = 1 – 5

The gas phase vibrational spectroscopy of cryogenically cooled C2n + 1N− anions with n = 1 − 5 is investigated in the spectral range of the C≡C and C≡N stretching modes (1850–2400 cm–1) by way of infrared photodissociation (IRPD) spectroscopy of messenger-tagged C2n+1N–· mD2 complexes. The IRPD spectra are assigned based on a comparison to previously reported anharmonic and harmonic CCSD(T) vibrational frequencies and intensities. Experimentally determined and predicted anharmonic vibrational transition energies lie within ± 21 cm–1. For the harmonic CCSD(T)/vqz+ vibrational frequencies a scaling factor of 0.9808 is determined, resulting in comparable absolute deviations. The influence of the D2-messenger molecules on the structure and the IRPD spectrum is found to be small. Compared to the results of previous IR matrix isolation studies additional, in particular weaker, IR-active transitions are identified