59 research outputs found
Cavity-Enhanced Two-Photon Interference using Remote Quantum Dot Sources
Quantum dots in cavities have been shown to be very bright sources of
indistinguishable single photons. Yet the quantum interference between two
bright quantum dot sources, a critical step for photon based quantum
computation, has never been investigated. Here we report on such a measurement,
taking advantage of a deterministic fabrication of the devices. We show that
cavity quantum electrodynamics can efficiently improve the quantum interference
between remote quantum dot sources: poorly indistinguishable photons can still
interfere with good contrast with high quality photons emitted by a source in
the strong Purcell regime. Our measurements and calculations show that cavity
quantum electrodynamics is a powerful tool for interconnecting several devices.Comment: 5 pages, 4 figures (Supp. Mat. attached
A unipolar quantum dot diode structure for advanced quantum light sources
Triggered, indistinguishable, single photons play a central role in various
quantum photonic implementations. Here, we realize a novel nin
diode structure embedding semiconductor quantum dots: the gated device enables
spectral tuning of the transitions and deterministic control of the observed
charged states. Blinking-free single-photon emission and high two-photon
indistinguishability is observed. The linewidth's temporal evolution is
investigated for timescales spanning more than orders of magnitude,
combining photon-correlation Fourier spectroscopy, high-resolution
photoluminescence spectroscopy, and two-photon interference (visibility of
and ). No spectral diffusion or decoherence on
timescales above is observed for most of the dots, and the
emitted photons' linewidth
deviates from the Fourier-transform limit only by a factor of . Thus, for
remote TPI experiments, visibilities above are anticipated. The presence
of n-doping only signifies higher available carrier mobility, making the
presented device highly attractive for future development of high-speed
tunable, high-performance quantum light sources
Entangling quantum-logic gate operated with an ultrabright semiconductor single-photon source
We demonstrate the unambiguous entangling operation of a photonic quantum-logic gate driven by an ultrabright solid-state single-photon source. Indistinguishable single photons emitted by a single semiconductor quantum dot in a micropillar optical cavity are used as target and control qubits. For a source brightness of 0.56 photons per pulse, the measured truth table has an overlap with the ideal case of 68.4 +/- 0.5%, increasing to 73.0 +/- 1.6% for a source brightness of 0.17 photons per pulse. The gate is entangling: At a source brightness of 0.48, the Bell-state fidelity is above the entangling threshold of 50% and reaches 71.0 +/- 3.6% for a source brightness of 0.15
Near optimal single photon sources in the solid state
Single-photons are key elements of many future quantum technologies, be it
for the realisation of large-scale quantum communication networks for quantum
simulation of chemical and physical processes or for connecting quantum
memories in a quantum computer. Scaling quantum technologies will thus require
efficient, on-demand, sources of highly indistinguishable single-photons.
Semiconductor quantum dots inserted in photonic structures are ultrabright
single photon sources, but the photon indistinguishability is limited by charge
noise induced by nearby surfaces. The current state of the art for
indistinguishability are parametric down conversion single-photon sources, but
they intrinsically generate multiphoton events and hence must be operated at
very low brightness to maintain high single photon purity. To date, no
technology has proven to be capable of providing a source that simultaneously
generates near-unity indistinguishability and pure single photons with high
brightness. Here, we report on such devices made of quantum dots in
electrically controlled cavity structures. We demonstrate on-demand, bright and
ultra-pure single photon generation. Application of an electrical bias on
deterministically fabricated devices is shown to fully cancel charge noise
effects. Under resonant excitation, an indistinguishability of
is evidenced with a . The photon
extraction of and measured brightness of make this source
times brighter than any source of equal quality. This new generation of
sources open the way to a new level of complexity and scalability in optical
quantum manipulation
Active dielectric antenna on chip for spatial light modulation
Integrated photonic resonators are widely used to manipulate light propagation in an evanescently-coupled
waveguide. While the evanescent coupling scheme works well for planar optical systems that are naturally
waveguide based, many optical applications are free-space based, such as imaging, display, holographics,
metrology and remote sensing. Here we demonstrate an active dielectric antenna as the interface device that
allows the large-scale integration capability of silicon photonics to serve the free-space applications. We
show a novel perturbation-base diffractive coupling scheme that allows a high-Q planer resonator to directly
interact with and manipulate free-space waves. Using a silicon-based photonic crystal cavity whose
resonance can be rapidly tuned with a p-i-n junction, a compact spatial light modulator with an extinction
ratio of 9.5 dB and a modulation speed of 150 MHz is demonstrated. Method to improve the modulation
speed is discussed.Air Force Office of Scientific Research (AFOSR grant FA9550-12-1-0261
Extent of non-publication in cohorts of studies approved by research ethics committees or included in trial registries
Background: The synthesis of published research in systematic reviews is essential when providing evidence to inform clinical and health policy decisionmaking. However, the validity of systematic reviews is threatened if journal publications represent a biased selection of all studies that have been conducted (dissemination bias). To investigate the extent of dissemination bias we conducted a systematic review that determined the proportion of studies published as peerreviewed journal articles and investigated factors associated with full publication in cohorts of studies (i) approved by research ethics committees (RECs) or (ii) included in trial registries. Copyright:Methods and Findings: Four bibliographic databases were searched for methodological research projects (MRPs) without limitations for publication year, language or study location. The searches were supplemented by handsearching the references of included MRPs. We estimated the proportion of studies published using prediction intervals (PI) and a random effects meta-analysis. Pooled odds ratios (OR) were used to express associations between study characteristics and journal publication. Seventeen MRPs (23 publications) evaluated cohorts of studies approved by RECs; the proportion of published studies had a PI between 22% and 72% and the weighted pooled proportion when combining estimates would be 46.2% (95% CI 40.2%-52.4%, I2594.4%). Twenty-two MRPs (22 publications) evaluated cohorts of studies included in trial registries; the PI of the proportion published ranged from 13% to 90% and the weighted pooled proportion would be 54.2% (95% CI 42.0%-65.9%, I2598.9%). REC-approved studies with statistically significant results (compared with those without statistically significant results) were more likely to be published (pooled OR 2.8; 95% CI 2.2-3.5). Phase-III trials were also more likely to be published than phase II trials (pooled OR 2.0; 95% CI 1.6- 2.5). The probability of publication within two years after study completion ranged from 7% to 30%.Conclusions: A substantial part of the studies approved by RECs or included in trial registries remains unpublished. Due to the large heterogeneity a prediction of the publication probability for a future study is very uncertain. Non-publication of research is not a random process, e.g., it is associated with the direction of study findings. Our findings suggest that the dissemination of research findings is biased
Lower bound for the spatial extent of localized modes in photonic-crystal waveguides with small random imperfections
Light localization due to random imperfections in periodic media is paramount in photonics research. The group index is known to be a key parameter for localization near photonic band edges, since small group velocities reinforce light interaction with imperfections. Here, we show that the size of the smallest localized mode that is formed at the band edge of a one-dimensional periodic medium is driven instead by the effective photon mass, i.e. the flatness of the dispersion curve. Our theoretical prediction is supported by numerical simulations, which reveal that photonic-crystal waveguides can exhibit surprisingly small localized modes, much smaller than those observed in Bragg stacks thanks to their larger effective photon mass. This possibility is demonstrated experimentally with a photonic-crystal waveguide fabricated without any intentional disorder, for which near-field measurements allow us to distinctly observe a wavelength-scale localized mode despite the smallness (∼1/1000 of a wavelength) of the fabrication imperfections
Dynamic vibronic coupling in InGaAs quantum dots
The electron-phonon coupling in self-assembled InGaAs quantum dots is relatively weak at low
light intensities, which means that the zero-phonon line in emission is strong compared to the phonon
sideband. However, the coupling to acoustic phonons can be dynamically enhanced in the presence
of an intense optical pulse tuned within the phonon sideband. Recent experiments have shown that
this dynamic vibronic coupling can enable population inversion to be achieved when pumping with a
blue-shifted laser and for rapid de-excitation of an inverted state with red detuning. In this paper we
confirm the incoherent nature of the phonon-assisted pumping process and explore the temperature
dependence of the mechanism. We also show that a combination of blue- and red-shifted pulses
can create and destroy an exciton within a timescale ∼ 20 ps determined by the pulse duration and
ultimately limited by the phonon thermalisation time
Viscum album L. extracts in breast and gynaecological cancers: a systematic review of clinical and preclinical research
<p>Abstract</p> <p>Background</p> <p><it>Viscum album </it>L. extracts (VAE, European mistletoe) are a widely used medicinal plant extract in gynaecological and breast-cancer treatment.</p> <p>Methods</p> <p>Systematic review to evaluate clinical studies and preclinical research on the therapeutic effectiveness and biological effects of VAE on gynaecological and breast cancer. Search of databases, reference lists and expert consultations. Criteria-based assessment of methodological study quality.</p> <p>Results</p> <p>19 randomized (RCT), 16 non-randomized (non-RCT) controlled studies, and 11 single-arm cohort studies were identified that investigated VAE treatment of breast or gynaecological cancer. They included 2420, 6399 and 1130 patients respectively. 8 RCTs and 8 non-RCTs were embedded in the same large epidemiological cohort study. 9 RCTs and 13 non-RCTs assessed survival; 12 reported a statistically significant benefit, the others either a trend or no difference. 3 RCTs and 6 non-RCTs assessed tumour behaviour (remission or time to relapse); 3 reported statistically significant benefit, the others either a trend, no difference or mixed results. Quality of life (QoL) and tolerability of chemotherapy, radiotherapy or surgery was assessed in 15 RCTs and 9 non-RCTs. 21 reported a statistically significant positive result, the others either a trend, no difference, or mixed results. Methodological quality of the studies differed substantially; some had major limitations, especially RCTs on survival and tumour behaviour had very small sample sizes. Some recent studies, however, especially on QoL were reasonably well conducted. Single-arm cohort studies investigated tumour behaviour, QoL, pharmacokinetics and safety of VAE. Tumour remission was observed after high dosage and local application. VAE application was well tolerated. 34 animal experiments investigated VAE and isolated or recombinant compounds in various breast and gynaecological cancer models in mice and rats. VAE showed increase of survival and tumour remission especially in mice, while application in rats as well as application of VAE compounds had mixed results. <it>In vitro </it>VAE and its compounds have strong cytotoxic effects on cancer cells.</p> <p>Conclusion</p> <p>VAE shows some positive effects in breast and gynaecological cancer. More research into clinical efficacy is warranted.</p
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