Efficient Approximation of Quantum Channel Capacities

We propose an iterative method for approximating the capacity of classical-quantum channels with a discrete input alphabet and a finite dimensional output, possibly under additional constraints on the input distribution. Based on duality of convex programming, we derive explicit upper and lower bounds for the capacity. To provide an $\varepsilon$-close estimate to the capacity, the presented algorithm requires $O(\tfrac{(N \vee M) M^3 \log(N)^{1/2}}{\varepsilon})$, where $N$ denotes the input alphabet size and $M$ the output dimension. We then generalize the method for the task of approximating the capacity of classical-quantum channels with a bounded continuous input alphabet and a finite dimensional output. For channels with a finite dimensional quantum mechanical input and output, the idea of a universal encoder allows us to approximate the Holevo capacity using the same method. In particular, we show that the problem of approximating the Holevo capacity can be reduced to a multidimensional integration problem. For families of quantum channels fulfilling a certain assumption we show that the complexity to derive an $\varepsilon$-close solution to the Holevo capacity is subexponential or even polynomial in the problem size. We provide several examples to illustrate the performance of the approximation scheme in practice.Comment: 36 pages, 1 figur

Sugammadex to reverse residual neuromuscular blockade and facilitate neurologic examination in an adolescent trauma patient in the Pediatric ICU setting.

Neuromuscular blocking agents (NMBAs) are frequently used in acute care scenarios to facilitate endotracheal in- tubation and permit effective mechanical ventilation. Despite their potential therapeutic efficacy, the immobil- ity may prevent clinical evaluation of a patient’s neuro- logic status. In specific clinical scenarios such as when immediate tracheal extubation is indicated or assessment of neurologic status is required, prompt reversal of neu- romuscular blockade may be indicated. We present the novel use of sugammadex for reversal of NM blockade to allow for neurologic examination and tracheal extubation in an adolescent trauma patient. The pharmacology of sugammadex is reviewed, reports of its use in pediatric- aged patients discussed, and potential scenarios for use in the ICU setting presented

Upper bound on the secret key rate distillable from effective quantum correlations with imperfect detectors

We provide a simple method to obtain an upper bound on the secret key rate that is particularly suited to analyze practical realizations of quantum key distribution protocols with imperfect devices. We consider the so-called trusted device scenario where Eve cannot modify the actual detection devices employed by Alice and Bob. The upper bound obtained is based on the available measurements results, but it includes the effect of the noise and losses present in the detectors of the legitimate users.Comment: 9 pages, 1 figure; suppress sifting effect in the figure, final versio

Experimental Comparison of Probabilistic Shaping Methods for Unrepeated Fiber Transmission

\u3cp\u3eThis paper studies the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-to-back configuration and in unrepeated nonlinear fiber transmissions. For the back-to-back setup, various shaped quadrature amplitude modulation (QAM) distributions are found to have the same implementation penalty as uniform input. By demonstrating in transmission experiments that shaped QAM input leads to lower effective SNR than uniform input at a fixed average launch power, we experimentally confirm that shaping enhances the fiber nonlinearities. However, shaping is ultimately found to increase the AIR, which is the most relevant figure of merit, as it is directly related to spectral efficiency. In a detailed study of these shaping gains for the nonlinear fiber channel, four strategies for optimizing QAM input distributions are evaluated and experimentally compared in wavelength division multiplexing (WDM) systems. The first shaping scheme generates a Maxwell-Boltzmann (MB) distribution based on a linear additive white Gaussian noise channel. The second strategy uses the Blahut-Arimoto algorithm to optimize an unconstrained QAM distribution for a split-step Fourier method based channel model. In the third and fourth approach, MB-shaped QAM and unconstrained QAM are optimized via the enhanced Gaussian noise (EGN) model. Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%. This general behavior is observed in 9-channel and fully loaded WDM experiments.\u3c/p\u3

One-way quantum key distribution: Simple upper bound on the secret key rate

We present a simple method to obtain an upper bound on the achievable secret key rate in quantum key distribution (QKD) protocols that use only unidirectional classical communication during the public-discussion phase. This method is based on a necessary precondition for one-way secret key distillation; the legitimate users need to prove that there exists no quantum state having a symmetric extension that is compatible with the available measurements results. The main advantage of the obtained upper bound is that it can be formulated as a semidefinite program, which can be efficiently solved. We illustrate our results by analysing two well-known qubit-based QKD protocols: the four-state protocol and the six-state protocol. Recent results by Renner et al., Phys. Rev. A 72, 012332 (2005), also show that the given precondition is only necessary but not sufficient for unidirectional secret key distillation.Comment: 11 pages, 1 figur

No Association of Variants of the NPY-System With Obsessive-Compulsive Disorder in Children and Adolescents

Obsessive-compulsive disorder (OCD) causes severe distress and is therefore counted by the World Health Organisation (WHO) as one of the 10 most impairing illnesses. There is evidence for a strong genetic underpinning especially in early onset OCD (eoOCD). Though several genes involved in neurotransmission have been reported as candidates, there is still a need to identify new pathways. In this study, we focussed on genetic variants of the Neuropeptide Y (NPY) system. NPY is one of the most abundant neuropeptides in the human brain with emerging evidence of capacity to modulate stress response, which is of high relevance in OCD. We focussed on tag-SNPs of NPY and its receptor gene NPY1R in a family-based approach. The sample comprised 86 patients (children and adolescents) with eoOCD with both their biological parents. However, this first study on genetic variants of the NPY-system could not confirm the association between the investigated SNPs and eoOCD. Based on the small sample size results have to be interpreted as preliminary and should be replicated in larger samples. However, also in an additional GWAS analysis in a large sample, we could not observe an associations between NPY and OCD. Overall, these preliminary results point to a minor role of NPY on the stress response of OCD

Langversion der interdisziplinären evidenz- und konsensbasierten S3-Leitlinie für Diagnostik und Therapie von Zwangsstörungen im Kindes- und Jugendalter

Zwangsstörungen gehören mit einer Langzeitprävalenz von 1-3% auch im Kindes- und Jugendalter zu den häufigsten psychischen Störungen. Es liegen zwei Erkrankungsgipfel im Altersbereich von 11-14 Jahren und im jungen Erwachsenenalter mit 20 Jahren vor. 20% der Zwangsstörungen beginnen vor dem Alter von 10 Jahren und 60% vor dem Alter von 25 Jahren. Die Erkrankung wird oftmals sehr spät erkannt. Es dauert im Durchschnitt über 10 Jahre bis die Patienten professionelle Hilfe aufsuchen. Es gibt einige behandlungsrelevante Unterschiede von Zwangsstörungen im Kindes- und Jugendalter im Vergleich zum Erwachsenenalter. In der Diagnostik und Behandlung müssen das Alter und der Entwicklungsstand der Betroffenen sowie die Bedingungen um familiären und sozialen Umfeld berücksichtigt werden. Die Fehl- und Unterdiagnosen sind im Kindes- und Jugendalter wie im Erwachsenenalter sehr hoch. Verlaufsstudien zeigen, dass die Erkrankung oft chronisch verläuft und zu einer erheblichen psychosozialen Beeinträchtigung führt. Auch ist das Risiko für die Entwicklung von weiteren psychischen, aber auch somatischen Störungen und Folgeerkrankungen hoch. Aus der Studienlage wird deutlich, dass der frühe Behandlungsbeginn einer der wichtigsten positiven prognostischen Faktoren ist (Walitza et al., 2020, Fineberg et al., 2019). Wegen der hohen Bedeutung der Früherkennung und frühen Interventionen wurde 2019 ein internationales Consensus-Statement verfasst (Fineberg et al., 2019) in welchem auch die Aspekte, die Kinder und Jugendliche betreffen, berücksichtigt werden. Zudem besteht eine Unterversorgung, diese kommt unter anderem zustande durch mangelnde Verfügbarkeit von einer anwendergerechten Zusammenfassung der Evidenz von Behandlungsansätzen im Rahmen einer Leitlinie für Diagnostik und Therapie im Kindes- und Jugendalter. Diese Gründe, aber auch das Ziel der breiten Disseminierung der Leitlinie zu allen Versorgern, die Kinder und Jugendliche sehen, ist Anlass und Grund für diese Leitlinie. Neben der Praxis und Anwendung selbst, ist eine Leitlinie auch relevant für die Aus- und Weiterbildung. Zum aktuellen Zeitpunkt werden die evidenzbasierten Therapien national und international nicht flächendeckend eingesetzt. Bislang gibt es für Zwangsstörungen im Kindes- und Jugendalter keine S3-Leitlinie. Ziel ist es die Diagnostik und Behandlung von Zwangsstörungen zu verbessern und den Therapeuten eine Leitlinie auf S3 Niveau an die Hand zu geben. Die Langversion der Leitlinie gibt zusätzlich eine Zusammenfassung des Hintergrundwissens zu Zwangsstörungen im Kindes- und Jugendalter und einen Teil der Diskussion im Konsentierungsprozess wieder, die neben der Evidenz und der Konsentierung ebenfalls hinter den Empfehlungen steht

Can Exercise Enhance the Efficacy of Checkpoint Inhibition by Modulating Anti-Tumor Immunity?

Immune checkpoint inhibition (ICI) has revolutionized cancer therapy. However, response to ICI is often limited to selected subsets of patients or not durable. Tumors that are non-responsive to checkpoint inhibition are characterized by low anti-tumoral immune cell infiltration and a highly immunosuppressive tumor microenvironment. Exercise is known to promote immune cell circulation and improve immunosurveillance. Results of recent studies indicate that physical activity can induce mobilization and redistribution of immune cells towards the tumor microenvironment (TME) and therefore enhance anti-tumor immunity. This suggests a favorable impact of exercise on the efficacy of ICI. Our review delivers insight into possible molecular mechanisms of the crosstalk between muscle, tumor, and immune cells. It summarizes current data on exercise-induced effects on anti-tumor immunity and ICI in mice and men. We consider preclinical and clinical study design challenges and discuss the role of cancer type, exercise frequency, intensity, time, and type (FITT) and immune sensitivity as critical factors for exercise-induced impact on cancer immunosurveillance