Quantum simulation of partially distinguishable boson sampling

Boson Sampling is the problem of sampling from the same output probability distribution as a collection of indistinguishable single photons input into a linear interferometer. It has been shown that, subject to certain computational complexity conjectures, in general the problem is difficult to solve classically, motivating optical experiments aimed at demonstrating quantum computational "supremacy". There are a number of challenges faced by such experiments, including the generation of indistinguishable single photons. We provide a quantum circuit that simulates bosonic sampling with arbitrarily distinguishable particles. This makes clear how distinguishabililty leads to decoherence in the standard quantum circuit model, allowing insight to be gained. At the heart of the circuit is the quantum Schur transform, which follows from a representation theoretic approach to the physics of distinguishable particles in first quantisation. The techniques are quite general and have application beyond boson sampling.Comment: 25 pages, 4 figures, 2 algorithms, comments welcom

A Pilot Study of the Effect of a Change in the Scheduling of Canadian Medical Licensing Examinations on Two Cohorts of Students Studying in Ireland

Background: The Medical Council of Canada and most Canadian residency programs require international medical graduates seeking training in Canada to pass the Medical Council of Canada Entrance Examination, in addition to the newly established National Collaborative Assessment. In order to facilitate this additional examination, the Medical Council of Canada has altered the suggested examination timeline and examination eligibility criteria. Methods: A cross-sectional survey was sent via an online survey tool to members of the North American Irish Medical Student Association. The survey aimed to elicit differences in the Medical Council of Canada Entrance Examination experience between two cohorts of Canadians studying abroad in Ireland: those who completed the examination before and after the new timeline. Statistical analysis was conducted with independent t-tests and Pearson’s Chi-Square tests using SPSS version 21. Results: Of 24 respondents, 13 had completed the examination after the timeline change. Participants who attended the examination prior to the change achieved higher results (353.8 ± 56.5) than participants who attended the examination after the change (342.3 ± 35.1), although not statistically significant (p=0.56). In the cohort who took the examination after the timeline change, 61.5% of participants expressed discontent with their examination results; 84.6% ‘strongly agreed’ or ‘agreed’ to feeling disadvantaged due to the change. Conclusion: The new Medical Council of Canada examination timeline has had an impact on the examination experience of Canadians studying in Ireland. Simple modifications to the current timeline are warranted to reduce unnecessary disadvantage for this cohort of students applying to postgraduate training..

Investigating functional and genetic interactions underlying schizophrenia risk in 22q11.2 Deletion Syndrome

22q11.2 Deletion Syndrome (22q11.2DS) is a genetic disorder caused by a hemizygous deletion at chromosome 22q11.2. It is the most common chromosomal microdeletion and the strongest known molecular genetic risk factor associated with schizophrenia. However, the underlying mechanisms that lead to this neuropsychiatric risk remain largely unknown. The work in this thesis sought to investigate possible genetic and functional mechanisms that contribute to schizophrenia risk in 22q.11.2DS. Potential schizophrenia candidate and disease modifier genes from within and outside of the 22q11.2 deletion region were explored. From within the deletion, DGCR8 was initially selected as a gene of interest due to its key role in the microRNA biogenesis pathway and therefore gene expression regulation. Additional candidate genes were identified by assessing gene co-expression during fetal development in relation to DGCR8 and predicated of loss of function and happloinsuffiency intolerance, leading to the selection of HIRA and ZDHHC8. Transcriptome wide association studies were performed in disease relevant tissues to identify schizophrenia modifier genes outside of the deletion by comparing 22q11.2DS patients with and without schizophrenia. However, this analysis identified no significant differences in gene expression. CRISPR/Cas9 genome editing technology was utilised to knockout DGCR8 in human embryonic stem cells. Mutant lines were generated and differentiated into cortical neuroprogenitor cells to investigate the role of DGCR8 in neurodevelopment. This work provided further evidence that DGCR8 knockout lines derived from human embryonic stem cells may not be a viable method of modelling due to genomic instability, lack of protein reduction and so insufficient disease recapitulation. Finally, a lentiviral based CRISPR/Cas9 system in human neuroprogenitor cells (hNPCs) was established. Genetic manipulation of DGCR8 in hNPCs further indicated a relationship between DGCR8 and TBR1 in cortical development. This thesis combines bioinformatic and cellular approaches to provide a basis for investigation of mechanisms underlying schizophrenia risk in 22q11.2DS

Classically simulating near-term partially-distinguishable and lossy boson sampling

Boson Sampling is the problem of sampling from the same distribution as indistinguishable single photons at the output of a linear optical interferometer. It is an example of a non-universal quantum computation which is believed to be feasible in the near term and cannot be simulated on a classical machine. Like all purported demonstrations of "quantum supremacy", this motivates optimizing classical simulation schemes for a realistic model of the problem, in this case Boson Sampling when the implementations experience lost or distinguishable photons. Although current simulation schemes for sufficiently imperfect boson sampling are classically efficient, in principle the polynomial runtime can be infeasibly large. In this work, we develop a scheme for classical simulation of Boson Sampling under uniform distinguishability and loss, based on the idea of sampling from distributions where at most k photons are indistinguishable. We show that asymptotically this scheme can provide a polynomial improvement in the runtime compared to classically simulating idealised Boson Sampling. More significantly, we show that in the regime considered experimentally relevant, our approach gives an substantial improvement in runtime over other classical simulation approaches.Comment: 15 pages, 5 figures, comments welcom

Clinical Presentation, Diagnostic Features, and Mortality in Dementia with Lewy Bodies.

BACKGROUND: Dementia with Lewy bodies (DLB) is the second most common degenerative dementia in older people. However, rates of misdiagnosis are high, and little is known of its natural history and outcomes. Very few previous studies have been able to access routine clinical information for large, unbiased DLB cohorts in order to establish initial presentation, neuropsychological profile, and mortality. OBJECTIVE: To examine in detail, symptom patterns at presentation and their association with outcomes, including mortality, in a large naturalistic DLB cohort from a secondary care sample. METHODS: A retrospective cohort design was used to identify a DLB cohort (n = 251) from Cambridgeshire and Peterborough NHS Foundation Trust (CPFT). Information relating to first consultation, diagnosis, and DLB diagnostic features were extracted. RESULTS: A wide range of presenting complaints and differential initial diagnoses were identified for the cohort. Along with memory loss (27.1%) and hallucinations (25.4%), low mood (25.1%) was noted as a key presenting complaint among the DLB cohort. Rates of REM sleep disorder were considerably lower (8.4%) than would be expected. Deficits in non-amnestic cognitive domains were associated with reduced mortality compared with amnestic-only presentations. CONCLUSION: Individuals later diagnosed with DLB present initially to secondary care with a wide range of symptoms and complaints, some of which are not immediately suggestive of a DLB diagnosis. More examinations of large cohorts such as this are needed to further elucidate the complex presentation and clinical course of DLB, and to confirm whether amnestic-only presentation confers a worse outcome.Alzheimer's Society; CPFT; NIHR Cambridge Biomedical Research Centr

The First Case of Catheter-related Bloodstream Infection Caused by Nocardia farcinica

Nocardia farcinica is an emerging pathogen in immunocompromised hosts. Even though several species of Nocardia have been reported as causative pathogens of catheter-related blood stream infections (CRBSI), CRBSI caused by N. farcinica has not been reported. A 70-yr-old man with a tunneled central venous catheter (CVC) for home parenteral nutrition was admitted with fever for two days. Norcardia species was isolated from the blood through CVC and peripheral bloods and identified to N. farcinica by 16S rRNA and rpoB gene sequence analyses. This report emphasizes the rapid and correct identification of causative agents in infectious diseases in the selection of antimicrobial agents and the consideration of catheter removal