Interpreting quantum discord through quantum state merging

We present an operational interpretation of quantum discord based on the quantum state merging protocol. Quantum discord is the markup in the cost of quantum communication in the process of quantum state merging, if one discards relevant prior information. Our interpretation has an intuitive explanation based on the strong subadditivity of von Neumann entropy. We use our result to provide operational interpretations of other quantities like the local purity and quantum deficit. Finally, we discuss in brief some instances where our interpretation is valid in the single copy scenario.Comment: 5 pages, no figures. See http://arxiv.org/abs/1008.3205 for similar results. Typos fixed, references and acknowledgements updated. End note adde

Antiviral treatment for Bell’s palsy (Idiopathic facial paralysis)

Background Corticosteroids are widely used in the treatment of idiopathic facial paralysis (Bell’s palsy), but the effectiveness of additional treatment with an antiviral agent is uncertain. This review was first published in 2001 and most recently updated in 2015. Since a significant benefit of corticosteroids for the early management of Bell’s palsy has been demonstrated, the main focus of this update, as in the previous version, was to determine the effect of adding antivirals to corticosteroid treatment. We undertook this update to integrate additional evidence and to better assess the robustness of findings, taking risk of bias fully into account. Objectives To assess the effects of antiviral treatments alone or in combination with any other therapy for Bell’s palsy. Search methods We searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, and LILACS in July 2019. We reviewed the bibliographies of the identified trials and contacted trial authors to identify additional published or unpublished data. We searched clinical trials registries for ongoing studies. Selection criteria We considered randomised controlled trials (RCTs) or quasi-RCTs of antivirals with and without corticosteroids versus control therapies for the treatment of Bell’s palsy. We excluded trials that followed-up participants for less than three months. Data collection and analysis We independently assessed trials for relevance, eligibility, and risk of bias, using standard Cochrane procedures. We performed sensitivity analyses excluding trials at high or unclear risk of bias in at least five domains, and reported these data as the primary analyses. Main results Fourteen trials, including 2488 participants, met the inclusion criteria. Most were small, and most were at high or unclear risk of bias in multiple domains. We included four new studies at this update. Incomplete recovery A combination of antivirals and corticosteroids may have little or no effect on rates of incomplete recovery in people with Bell’s palsy compared to corticosteroids alone (risk ratio (RR) 0.81, 95% confidence interval (CI) 0.38 to 1.74; 3 trials, N = 766; random-effects; low-certainty evidence). We excluded 10 trials that were at high or unclear risk of bias in several domains from this analysis and limited all analyses to studies at lower risk of bias. Recovery rates were better in participants receiving corticosteroids alone than antivirals alone (RR 2.69, 95% CI 0.73 to 10.01; 2 trials, N = 667; random-effects), but the result was imprecise and allowed for the possibility of no effect. The rate of incomplete recovery was lower with antivirals plus corticosteroids than with placebo or no treatment (RR 0.56, 95% CI 0.42 to 0.76; 2 trials, N = 658; random-effects). Antivirals alone had no clear effect on incomplete recovery rates compared with placebo, but the result was imprecise (RR 1.10, 95% CI 0.87 to 1.40; 2 trials, N = 658; fixed-effect). For people with severe Bell’s palsy (House-Brackmann score of 5 and 6, or equivalent on other scales), we found that the combination of antivirals and corticosteroids had no clear effect on incomplete recovery at month six compared to corticosteroids alone, although the result was again imprecise (RR 0.82, 95% CI 0.57 to 1.17; 2 trials, N = 98; random-effects). Motor synkinesis or crocodile tears Antivirals plus corticosteroids reduced the proportion of participants who experienced these long-term sequelae from Bell’s palsy compared to placebo plus corticosteroids (RR 0.56, 95% CI 0.36 to 0.87; 2 trials, N = 469; fixed-effect; moderate-certainty evidence). Antivirals plus corticosteroids reduced long-term sequelae compared to placebo but there was no clear difference in this outcome with antivirals alone compared to placebo. Adverse events Adverse event data were available in four studies providing data on 1592 participants. None of the four comparisons showed clear differences in adverse events between treatment and comparison arms (very low-certainty evidence); for the comparison of antivirals plus corticosteroids and corticosteroids alone in studies at lower risk of bias, the RR was 1.17 (95% CI 0.81 to 1.69; 2 trials, N = 656; fixed-effect; very low-certainty evidence). Authors’ conclusions The combination of antivirals and corticosteroids may have little or no effect on rates of incomplete recovery in comparison to corticosteroids alone in Bell’s palsy of various degrees of severity, or in people with severe Bell’s palsy, but the results were very imprecise. Corticosteroids alone were probably more effective than antivirals alone and antivirals plus corticosteroids were more effective than placebo or no treatment. There was no clear benefit from antivirals alone over placebo. The combination of antivirals and corticosteroids probably reduced the late sequelae of Bell’s palsy compared with corticosteroids alone. Studies also showed fewer episodes of long-term sequelae in corticosteroid-treated participants than antiviral-treated participants. We found no clear difference in adverse events from the use of antivirals compared with either placebo or corticosteroids, but the evidence is too uncertain for us to draw conclusions. An adequately powered RCT in people with Bell’s palsy that compares different antiviral agents may be indicated.Publisher PDFPeer reviewe

Gastric Fistula in the Chest After Sleeve Gastrectomy: a Systematic Review of Diagnostic and Treatment Options

This study aimed to establish the optimal diagnostic and treatment algorithm for the management of gastric fistula in the chest (GFIC) after sleeve gastrectomy (SG) through a systematic review of published cases. A multi-database search was performed, which produced 1182 results, of which 26 studies were included in this systematic review. The initial presentation included subphrenic collections, leaks, or (recurrent) pneumonia with associated symptoms such as persistent cough, fever, and/or dyspnea. Computed tomography (CT) scan in combination with either upper gastrointestinal (UGI) series or an esophagogastroduodenoscopy (EGD) was used to adequately diagnose the fistulas. Initial treatment was either with clips and/or clips and stents that were placed endoscopically. When unsuccessful in the majority of the cases, the surgical treatment consisted of total gastrectomy and Roux-en-Y esophagojejunostomy in a laparoscopic or open fashion

Corticosteroids for Bell's palsy (idiopathic facial paralysis)

Background: Inflammation and oedema of the facial nerve are implicated in causing Bell's palsy. Corticosteroids have a potent anti-inflammatory action that should minimise nerve damage. This is an update of a review first published in 2002 and last updated in 2010. Objectives: To determine the effectiveness and safety of corticosteroid therapy in people with Bell's palsy. Search Methods: On 4 March 2016, we searched the Cochrane Neuromuscular Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and LILACS. We reviewed the bibliographies of the randomised trials and contacted known experts in the field to identify additional published or unpublished trials. We also searched clinical trials registries for ongoing trials. Selection criteria: Randomised trials and quasi-randomised trials comparing different routes of administration and dosage schemes of corticosteroid or adrenocorticotrophic hormone therapy versus a control group receiving no therapy considered effective for this condition, unless the same therapy was given in a similar way to the experimental group. Data collection and analysis: We used standard Cochrane methodology. The main outcome of interest was incomplete recovery of facial motor function (i.e. residual facial weakness). Secondary outcomes were cosmetically disabling persistent sequelae, development of motor synkinesis or autonomic dysfunction (i.e. hemifacial spasm, crocodile tears) and adverse effects of corticosteroid therapy manifested during follow-up. Main results: We identified seven trials, with 895 evaluable participants for this review. All provided data suitable for the primary outcome meta-analysis. One of the trials was new since the last version of this Cochrane systematic review. Risk of bias in the older, smaller studies included some unclear- or high-risk assessments, whereas we deemed the larger studies at low risk of bias. Overall, 79/452 (17%) participants allocated to corticosteroids had incomplete recovery of facial motor function six months or more after randomisation; significantly fewer than the 125/447 (28%) in the control group (risk ratio (RR) 0.63, 95% confidence interval (CI) 0.50 to 0.80, seven trials, n = 895). The number of people who need to be treated with corticosteroids to avoid one incomplete recovery was 10 (95% CI 6 to 20). The reduction in the proportion of participants with cosmetically disabling sequelae six months after randomisation was very similar in the corticosteroid and placebo groups (RR 0.96, 95% CI 0.40 to 2.29, two trials, n = 75, low-quality evidence). However, there was a significant reduction in motor synkinesis during follow-up in participants receiving corticosteroids (RR 0.64, 95% CI 0.45 to 0.91, three trials, n = 485, moderate-quality evidence). Three studies explicitly recorded the absence of adverse effects attributable to corticosteroids. One trial reported that three participants receiving prednisolone had temporary sleep disturbances and two trials gave a detailed account of adverse effects occurring in 93 participants, all non-serious; the combined analysis of data from these three trials found no significant difference in adverse effect rates between people receiving corticosteroids and people receiving placebo (RR 1.04, 95% CI 0.71 to 1.51, n = 715). Author's conclusions: The available moderate- to high-quality evidence from randomised controlled trials showed significant benefit from treating Bell's palsy with corticosteroids.Publisher PDFPeer reviewe

Splenic Abscess Following Sleeve Gastrectomy: A Systematic Review of Clinical Presentation and Management Methods

BACKGROUND: Splenic abscess is a rare complication following sleeve gastrectomy. METHODS: We performed a systematic review to clarify its clinical significance, presentation, and management. PubMed, Embase, MEDLINE, Google Scholar, and the Cochrane Library were searched up to the 19th of July 2020. A total of 18 patients were included, of which 11 were female and 7 were male. The mean age was 34.1 ± 12.3 years, and the mean body mass index was 45.8 ± 7.6 kg/m2. Type 2 diabetes mellitus was reported in 11.1% of patients and hypertension in 22.2%. Fever was the most common presenting symptom seen in 17 (94.4%) patients, followed by abdominal pain in 10 (55.6%). The mean duration from surgery to presentation was 98.6 ± 132.7 days (range 10–547 days). Computed tomography was used for investigations in 17/18 (94.4%) patients. Seven patients had reported leak, three reported bleeding, and 2 reported pleural effusion. Thirteen patients had unilocular abscess. All patients were treated with antibiotics. Four patients needed total parenteral nutrition, and three were given proton pump inhibitor. In total, 11 patients needed percutaneous drainage as a part of treatment and 11 patients needed total splenectomy and 1 needed partial splenectomy. CONCLUSION: Splenic abscess following sleeve gastrectomy is a rare identity. The etiology of formation of splenic abscess needs further studies. A computed tomography of the abdomen with contrast is the preferred diagnostic tool. There is no gold standard treatment for splenic abscess

Operational Significance of Discord Consumption: Theory and Experiment

Coherent interactions that generate negligible entanglement can still exhibit unique quantum behaviour. This observation has motivated a search beyond entanglement for a complete description of all quantum correlations. Quantum discord is a promising candidate. Here, we demonstrate that under certain measurement constraints, discord between bipartite systems can be consumed to encode information that can only be accessed by coherent quantum interactions. The inability to access this information by any other means allows us to use discord to directly quantify this `quantum advantage'. We experimentally encode information within the discordant correlations of two separable Gaussian states. The amount of extra information recovered by coherent interaction is quantified and directly linked with the discord consumed during encoding. No entanglement exists at any point of this experiment. Thus we introduce and demonstrate an operational method to use discord as a physical resource.Comment: 10 pages, 3 figures, updated with Nature Physics Reference, simplified proof in Appendi

Negativity and quantum discord in Davies environments

We investigate the time evolution of negativity and quantum discord for a pair of non-interacting qubits with one being weakly coupled to a decohering Davies--type Markovian environment. At initial time of preparation, the qubits are prepared in one of the maximally entangled pure Bell states. In the limiting case of pure decoherence (i.e. pure dephasing), both, the quantum discord and negativity decay to zero in the long time limit. In presence of a manifest dissipative dynamics, the entanglement negativity undergoes a sudden death at finite time while the quantum discord relaxes continuously to zero with increasing time. We find that in dephasing environments the decay of the negativity is more propitious with increasing time; in contrast, the evolving decay of the quantum discord proceeds weaker for dissipative environments. Particularly, the slowest decay of the quantum discord emerges when the energy relaxation time matches the dephasing time.Comment: submitted for publicatio

The classical-quantum boundary for correlations: discord and related measures

One of the best signatures of nonclassicality in a quantum system is the existence of correlations that have no classical counterpart. Different methods for quantifying the quantum and classical parts of correlations are amongst the more actively-studied topics of quantum information theory over the past decade. Entanglement is the most prominent of these correlations, but in many cases unentangled states exhibit nonclassical behavior too. Thus distinguishing quantum correlations other than entanglement provides a better division between the quantum and classical worlds, especially when considering mixed states. Here we review different notions of classical and quantum correlations quantified by quantum discord and other related measures. In the first half, we review the mathematical properties of the measures of quantum correlations, relate them to each other, and discuss the classical-quantum division that is common among them. In the second half, we show that the measures identify and quantify the deviation from classicality in various quantum-information-processing tasks, quantum thermodynamics, open-system dynamics, and many-body physics. We show that in many cases quantum correlations indicate an advantage of quantum methods over classical ones.Comment: Close to the published versio

Frozen and Invariant Quantum Discord under Local Dephasing Noise

In this chapter, we intend to explore and review some remarkable dynamical properties of quantum discord under various different open quantum system models. Specifically, our discussion will include several concepts connected to the phenomena of time invariant and frozen quantum discord. Furthermore, we will elaborate on the relation of these two phenomena to the non-Markovian features of the open system dynamics and to the usage of dynamical decoupling protocols.Comment: 29 pages, 8 figure