Memory effects and geometrical considerations in open quantum systems

This thesis discusses memory effects in open quantum systems with an emphasis on the Breuer, Laine, Piilo (BLP) measure of non-Markovianity. It is shown how the calculation of the measure can be simplifed and how quantum information protocols can bene t from memory e ects. The superdense coding protocol is used as an example of this. The quantum Zeno effect will also be studied from the point of view of memory e ects. Finally the geometric ideas used in simplifying the calculation of the BLP measure are applied in studying the amount of resources needed for detecting bipartite quantum correlations. It is shown that to decide without prior information if an unknown quantum state is entangled or not, an informationally complete measurement is required. The first part of the thesis contains an introduction to the theoretical ideas such as quantum states, closed and open quantum systems and necessary mathematical tools. The theory is then applied in the second part of the thesis as the results obtained in the original publications I-VI are presented and discussed.Tämä väitöskirja käsittelee muisti-ilmiöitä avoimissa kvanttisysteemeissä keskittyen erityisesti Breuer, Laine, Piilo (BLP) ei-markovisuus-mittaan.Työssä osoitetaan, miten mitan laskemista voidaan helpottaa ja miten kvantti-informaatioprotokollat voisivat hyötyä muistiefekteistä. Esimerkkinä tästä käytetään niin sanottua supertiheää koodausta. Myös Zeno-ilmiötä tutkitaan muisti-ilmiöiden näkökulmasta. Lopuksi mitan laskemisen helpottamisessa käytettyjä menetelmiä sovelletaan kvanttikorrelaatioiden olemassaolon osoittamiseen vaadittavien resurssien määrän tutkimiseen. Työssä näytetään, että ilman ennakkotietoja tuntemattoman kvanttitilan kietoutuneisuuden osoittaminen vaatii informatiivisesti täydellisiä mittauksia. Työn ensimmäisessä osassa esitellään teoreettisia käsitteitä kuten kvanttitiloja, suljettuja ja avoimia kvanttisysteemejä sekä tarvittavia matemaattisia työkaluja. Työn toisessa osassa osajulkaisuissa I-VI saadut tulokset esitellään ja teoriatyökaluja sovelletaan.Siirretty Doriast

Verifying the quantumness of bipartite correlations

Entanglement is at the heart of most quantum information tasks, and therefore considerable effort has been made to find methods of deciding the entanglement content of a given bipartite quantum state. Here, we prove a fundamental limitation to deciding if an unknown state is entangled or not: we show that any quantum measurement which can answer this question necessarily gives enough information to identify the state completely. Therefore, only prior information regarding the state can make entanglement detection less expensive than full state tomography in terms of the demanded quantum resources. We also extend our treatment to other classes of correlated states by considering the problem of deciding if a state is NPT, discordant, or fully classically correlated. Remarkably, only the question related to quantum discord can be answered without resorting to full state tomography

Efficient superdense coding in the presence of non-Markovian noise

Many quantum information tasks rely on entanglement, which is used as a resource, for example, to enable efficient and secure communication. Typically, noise, accompanied by loss of entanglement, reduces the efficiency of quantum protocols. We develop and demonstrate experimentally a superdense coding scheme with noise, where the decrease of entanglement in Alice's encoding state does not reduce the efficiency of the information transmission. Having almost fully dephased classical two-photon polarization state at the time of encoding with concurrence $0.163\pm0.007$, we reach values of mutual information close to $1.52\pm 0.02$ ($1.89\pm 0.05$) with 3-state (4-state) encoding. This high efficiency relies both on non-Markovian features, that Bob exploits just before his Bell-state measurement, and on very high visibility ($99.6\%\pm0.1\%$) of the Hong-Ou-Mandel interference within the experimental set-up. Our proof-of-principle results with measurements on mutual information pave the way for exploiting non-Markovianity to improve the efficiency and security of quantum information processing tasks.Comment: 6 pages, 4 figures. V2: Minor change

Tekoäly radiologiassa

Erilaiset tekoälymenetelmät kehittyvät nopeasti, ja niiden käyttö myös lääketieteessä lisääntyy. Syväoppimisessa (deep learning) voidaan käyttää yhä laajempia (syvempiä) hermoverkkoja, jotka mahdollistavat aikaisempaa monimutkaisempien tehtävien ratkaisemisen. Teknisen kehityksen ansiosta tekoälytutkimus onkin nykyisin mahdollista myös yksittäisissä akateemisissa keskuksissa ilman mittavia kustannuksia. Radiologian alalla tekoälymenetelmien tutkimus on lisääntynyt viime vuosina eksponentiaalisesti. Suurin osa menetelmistä liittyy kuvien automaattiseen analysointiin, kuten poikkeavien löydösten tunnistukseen ja luokitteluun sekä rakenteiden segmentointiin. Tekoälymenetelmät tuskin korvaavat radiologin tekemää työtä lähitulevaisuudessa, mutta ne voivat tehostaa toimintaa ja vähentää inhimillisiä virheitä.</p

Documentation of the patient's smoking status in common chronic diseases - analysis of medical' narrative reports using the ULMFiT based text classification

Introduction: Smoking cessation is essential part of a successful treatment in many chronic diseases. Our aim was to analyse how actively clinicians discuss and document patients' smoking status into electronic health records (EHR) and deliver smoking cessation assistance.Methods: We analysed the results using a combination of rule and deep learning-based algorithms. Narrative reports of all adult patients, whose treatment started between years 2010 and 2016 for one of seven common chronic diseases, were followed for two years. Smoking related sentences were first extracted with a rule-based algorithm. Subsequently, pre-trained ULMFiT-based algorithm classified each patient's smoking status as a current smoker, ex-smoker, or never smoker. A rule-based algorithm was then again used to analyse the physician-patient discussions on smoking cessation among current smokers.Results: A total of 35,650 patients were studied. Of all patients, 60% were found to have a smoking status in EHR and the documentation improved over time. Smoking status was documented more actively among COPD (86%) and sleep apnoea (83%) patients compared to patients with asthma, type 1&2 diabetes, cerebral infarction and ischemic heart disease (range 44-61%). Of the current smokers (N=7,105), 49% had discussed smoking cessation with their physician. The performance of ULMFiT-based classifier was good with F-scores 79-92.Conclusion: Ee found that smoking status was documented in 60% of patients with chronic disease and that the clinician had discussed smoking cessation in 49% of patients who were current smokers. ULMFiT-based classifier showed good/excellent performance and allowed us to efficiently study a large number of patients' medical narratives.</p

Associations Between IFI44L Gene Variants and Rates of Respiratory Tract Infections During Early Childhood

Background. Genetic heterogeneity in type I interferon (IFN)-related gene IFI44L may account for variable susceptibility to respiratory tract infections (RTIs) in children. Methods. In 2 prospective, population-based birth cohorts, the STEPS Study and the FinnBrain Birth Cohort Study, IFI44L genotypes for rs273259 and rs1333969 were determined in relation to the development of RTIs until 1 or 2 years of age, respectively. At age 3 months, whole-blood transcriptional profiles were analyzed and nasal samples were tested for respiratory viruses in a subset of children. Results. In the STEPS Study (n=1135), IFI44L minor/minor gene variants were associated with lower rates of acute otitis media episodes (adjusted incidence rate ratio, 0.77 [95% confidence interval, .61-.96] for rs273259 and 0.74 [.55-.99] for rs1333969) and courses of antibiotics for RTIs (0.76 [.62-.95] and 0.73 [.56-.97], respectively. In the FinnBrain cohort (n=971), IFI44L variants were associated with lower rates of RTIs and courses of antibiotics for RTIs. In respiratory virus-positive 3-month-old children, IFI44L gene variants were associated with decreased expression levels of IFI44L and several other IFN-related genes. Conclusions. Variant forms of IFI44L gene were protective against early-childhood RTIs or acute otitis media, and they attenuated IFN pathway activation by respiratory viruses.Peer reviewe

Health care resource utilization and characteristics of patients with eosinophilic asthma in secondary health care in Finland

Background: Eosinophilic airway inflammation is common in asthma patients and appears to be associated with severe exacerbations and loss of asthma control.Objective: To describe the resource utilization and clinical characteristics of patients with eosinophilic asthma.Design: Asthma patients >= 18 years with >= 1 blood eosinophil count in secondary care (South West Finland) during 2003. 2013 were included. Clinical characteristics (age, lung function, body mass index, and comorbidities) and asthma-related resource utilization (hospital admissions, outpatient visits, and emergency room [ER] visits) were retrieved. Resource utilization rates were compared for patients with blood eosinophil 300 cells/mu L, using adjusted negative binomial regression models.Results: Overall, 4,357 eligible patients were identified (mean age 60 years, females 68%), of which 1,927 (44%) had > 300 eosinophil cells/mu L blood. Patients with 300 eosinophil counts, exhibited similar clinical characteristics, including advanced age, poor lung function, and overweight. Comorbidities such as pneumonia, sinusitis, and nasal polyps, were more frequent among those with > 300 eosinophil cells/mu L blood compared with patients with lower counts. Eosinophil counts > 300 cells/mu L were associated with greater hospital admissions (rate ratio [RR] [95% confidence interval CI]: 1.13 [1.02; 1.24]) and outpatient visits (RR [95% CI]: 1.11 [1.03; 1.20]) compared with patients with lower eosinophil counts. Rates of ER visits were similar between the patient groups (RR [95% CI]: 0.99 [0.87; 1.12]).Conclusions: Hospital admissions and outpatient visits occurred more often for patients with eosinophil counts > 300 cells/mu L, than for patients with lower eosinophil counts. Routine blood eosinophil screening might be useful to identify patients with an eosinophilic phenotype eligible for more targeted treatments