Quantum Walks of Correlated Photons Peruzzo, Alberto; Lobino, Mirko; Matthews, Jonathan C.F ...
Science (American Association for the Advancement of Science),
09/2010, Volume:
329, Issue:
5998
Journal Article
Peer reviewed
Open access
Quantum walks of correlated particles offer the possibility of studying large-scale quantum interference; simulating biological, chemical, and physical systems; and providing a route to universal ...quantum computation. We have demonstrated quantum walks of two identical photons in an array of 21 continuously evanescently coupled waveguides in a SiOxNy chip. We observed quantum correlations, violating a classical limit by 76 standard deviations, and found that the correlations depended critically on the input state of the quantum walk. These results present a powerful approach to achieving quantum walks with correlated particles to encode information in an exponentially larger state space.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Shor's Quantum Factoring Algorithm on a Photonic Chip Politi, Alberto; Matthews, Jonathan C.F; O'Brien, Jeremy L
Science (American Association for the Advancement of Science),
09/2009, Volume:
325, Issue:
5945
Journal Article
Peer reviewed
Open access
Shor's quantum factoring algorithm finds the prime factors of a large number exponentially faster than any other known method, a task that lies at the heart of modern information security, ...particularly on the Internet. This algorithm requires a quantum computer, a device that harnesses the massive parellism afforded by quantum superposition and entanglement of quantum bits (or qubits). We report the demonstration of a compiled version of Shor's algorithm on an integrated waveguide silica-on-silicon chip that guides four single-photon qubits through the computation to factor 15.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Abstract
This paper presents a study of circumstellar debris around Sun-like stars using data from the Herschel DEBRIS Key Programme. DEBRIS is an unbiased survey comprising the nearest ∼90 stars of ...each spectral type A-M. Analysis of the 275 F-K stars shows that excess emission from a debris disc was detected around 47 stars, giving a detection rate of 17.1$^{+2.6}_{-2.3}$ per cent, with lower rates for later spectral types. For each target a blackbody spectrum was fitted to the dust emission to determine its fractional luminosity and temperature. The derived underlying distribution of fractional luminosity versus blackbody radius in the population showed that most detected discs are concentrated at f ∼ 10−5 and at temperatures corresponding to blackbody radii 7–40 au, which scales to ∼40 au for realistic dust properties (similar to the current Kuiper belt). Two outlying populations are also evident; five stars have exceptionally bright emission ( f > 5 × 10−5), and one has unusually hot dust <4 au. The excess emission distributions at all wavelengths were fitted with a steady-state evolution model, showing that these are compatible with all stars being born with a narrow belt that then undergoes collisional grinding. However, the model cannot explain the hot dust systems – likely originating in transient events – and bright emission systems – arising potentially from atypically massive discs or recent stirring. The emission from the present-day Kuiper belt is predicted to be close to the median of the population, suggesting that half of stars have either depleted their Kuiper belts (similar to the Solar system) or had a lower planetesimal formation efficiency.
On-chip integrated photonic circuits are crucial to further progress towards quantum technologies and in the science of quantum optics. Here we report precise control of single photon states and ...multiphoton entanglement directly on-chip. We manipulate the state of path-encoded qubits using integrated optical phase control based on resistive elements, observing an interference contrast of 98.2 ± 0.3%. We demonstrate integrated quantum metrology by observing interference fringes with two- and four-photon entangled states generated in a waveguide circuit, with respective interference contrasts of 97.2 ± 0.4% and 92 ± 4%, sufficient to beat the standard quantum limit. Finally, we demonstrate a reconfigurable circuit that continuously and accurately tunes the degree of quantum interference, yielding a maximum visibility of 98.2 ± 0.9%. These results open up adaptive and fully reconfigurable photonic quantum circuits not just for single photons, but for all quantum states of light.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Orthopedic infections are typically treated with intravenous antibiotics. In this trial, 1054 participants with complex orthopedic infections were assigned to receive either oral or intravenous ...antibiotics for the first 6 weeks of treatment. At 1 year, oral therapy was noninferior to intravenous therapy.
Major depressive disorder is associated with raised peripheral inflammatory markers. Mounting evidence also suggests that inflammation is involved in suicidal behavior. However, the involvement of ...inflammation in the brains of individuals with depression, and its association with suicidal ideation, needs further clarification. Translocator protein (TSPO), which is upregulated in activated glia (predominantly microglia), can be measured as an indication of neuroinflammation in vivo using positron emission tomography and TSPO-specific radioligands.
We used 11C(R)-PK11195 positron emission tomography to compare TSPO availability in the anterior cingulate cortex (ACC), prefrontal cortex, and insula between 14 medication-free patients in a major depressive episode of at least moderate severity and 13 matched healthy control subjects. In a post hoc analysis, we also compared TSPO availability between patients with and without suicidal thoughts.
Multivariate analysis of variance indicated significantly higher TSPO in patients compared with control subjects (p = .005). The elevation was of large effect size and significant in the ACC (p = .022, Cohen’s d = 0.95), with smaller nonsignificant elevations in the prefrontal cortex (p = .342, Cohen’s d = 0.38) and insula (p = .466, Cohen’s d = 0.29). TSPO was not elevated in patients without suicidal thinking but was significantly increased in those with suicidal thoughts compared with those without, most robustly in the ACC (p = .008) and insula (p = .023).
We confirm evidence for increased TSPO availability, suggestive of predominantly microglial activation, in the ACC during a moderate to severe major depressive episode. Our findings provide further incentive for evaluating anti-inflammatory therapies in major depressive disorder.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Objective
To describe differences in outcomes between pregnant women with and without coronavirus dsease 2019 (COVID‐19).
Design
Prospective cohort study of pregnant women consecutively admitted for ...delivery, and universally tested via nasopharyngeal (NP) swab for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) using reverse transcription–polymerase chain reaction. All infants of mothers with COVID‐19 underwent SARS‐CoV‐2 testing.
Setting
Three New York City hospitals.
Population
Pregnant women >20 weeks of gestation admitted for delivery.
Methods
Data were stratified by SARS‐CoV‐2 result and symptomatic status, and were summarised using parametric and nonparametric tests.
Main outcome measures
Prevalence and outcomes of maternal COVID‐19, obstetric outcomes, neonatal SARS‐CoV‐2, placental pathology.
Results
Of 675 women admitted for delivery, 10.4% were positive for SARS‐CoV‐2, of whom 78.6% were asymptomatic. We observed differences in sociodemographics and comorbidities among women with symptomatic COVID‐10 versus asymptomatic COVID‐19 versus no COVID‐19. Caesarean delivery rates were 46.7% in symptomatic COVID‐19, 45.5% in asymptomatic COVID‐19 and 30.9% in women without COVID‐19 (P = 0.044). Postpartum complications (fever, hypoxia, readmission) occurred in 12.9% of women with COVID‐19 versus 4.5% of women without COVID‐19 (P < 0.001). No woman required mechanical ventilation, and no maternal deaths occurred. Among 71 infants tested, none were positive for SARS‐CoV‐2. Placental pathology demonstrated increased frequency of fetal vascular malperfusion, indicative of thrombi in fetal vessels, in women with COVID‐19 versus women without COVID‐19 (48.3% versus 11.3%, P < 0.001).
Conclusion
Among pregnant women with COVID‐19 at delivery, we observed increased caesarean delivery rates and increased frequency of maternal complications in the postpartum period. Additionally, intraplacental thrombi may have maternal and fetal implications for COVID‐19 remote from delivery.
Tweetable
COVID‐19 at delivery: more caesarean deliveries, postpartum complications and intraplacental thrombi.
Tweetable
COVID‐19 at delivery: more caesarean deliveries, postpartum complications and intraplacental thrombi.
This article includes Author Insights, a video available at https://vimeo.com/rcog/authorinsights16403
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Quantum computers promise to solve certain problems that are forever intractable to classical computers. The first of these devices are likely to tackle bespoke problems suited to their own ...particular physical capabilities. Sampling the probability distribution from many bosons interfering quantum-mechanically is conjectured to be intractable to a classical computer but solvable with photons in linear optics. However, the complexity of this type of problem means its solution is mathematically unverifiable, so the task of establishing successful operation becomes one of gathering sufficiently convincing circumstantial or experimental evidence. Here, we develop scalable methods to experimentally establish correct operation for this class of computation, which we implement for three, four and five photons in integrated optical circuits, on Hilbert spaces of up to 50,000 dimensions. Our broad approach is practical for all quantum computational architectures where formal verification methods for quantum algorithms are either intractable or unknown.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
PDF
