11 research outputs found
Quantum Nature of Light Measured With a Single Detector
We realized the most fundamental quantum optical experiment to prove the
non-classical character of light: Only a single quantum emitter and a single
superconducting nanowire detector were used. A particular appeal of our
experiment is its elegance and simplicity. Yet its results unambiguously
enforce a quantum theory for light. Previous experiments relied on more complex
setups, such as the Hanbury-Brown-Twiss configuration, where a beam splitter
directs light to two photodetectors, giving the false impression that the beam
splitter is required. Our work results in a major simplification of the widely
used photon-correlation techniques with applications ranging from quantum
information processing to single-molecule detection.Comment: 7 page
Flexible Work Time in Germany: Do Workers Like it and How Have Employers Exploited it Over the Cycle?
One- and two-dimensional photonic crystal micro-cavities in single crystal diamond
The development of solid-state photonic quantum technologies is of great
interest for fundamental studies of light-matter interactions and quantum
information science. Diamond has turned out to be an attractive material for
integrated quantum information processing due to the extraordinary properties
of its colour centres enabling e.g. bright single photon emission and spin
quantum bits. To control emitted photons and to interconnect distant quantum
bits, micro-cavities directly fabricated in the diamond material are desired.
However, the production of photonic devices in high-quality diamond has been a
challenge so far. Here we present a method to fabricate one- and
two-dimensional photonic crystal micro-cavities in single-crystal diamond,
yielding quality factors up to 700. Using a post-processing etching technique,
we tune the cavity modes into resonance with the zero phonon line of an
ensemble of silicon-vacancy centres and measure an intensity enhancement by a
factor of 2.8. The controlled coupling to small mode volume photonic crystal
cavities paves the way to larger scale photonic quantum devices based on
single-crystal diamond
Investigation, manipulation, and coupling of single nanoscopic and quantum emitters
Die hier vorgelegte Dissertation beschäftigt sich mit Untersuchungen an nanoskopischen Emittern und den Möglichkeiten, deren Fluoreszenzverhalten durch kontrollierte Ankopplung an photonische und plasmonische Strukturen zu beeinflussen. Zum einen werden mit Ytterbium- und Erbium-Ionen kodotierte NaYF4 -Nanokristalle untersucht, die hervorragende Eigenschaften bei der Umwandlung von niederenergetischen Photonen in solche höherer Energie besitzen. Das so entstehende Fluoreszenzlicht einer Ansammlung von Nanokristallen wird auf seine Abhängigkeit von der Anregungsintensität untersucht. Mit der Hilfe eines Rasterkraftmikroskops (AFM) wird eine Abhängigkeit der spektralen Zusammensetzung des Fluoreszenzlichts einzelner Nanokristalle von deren Größe im Bereich von wenigen bis 50 nm aufgezeigt. Durch gezielte Manipulation mit dem AFM werden ebenfalls einzelne Nanokristalle an Goldnanokügelchen gekoppelt und die Mechanismen der beobachteten plasmonischen Verstärkung der Emission durch zeitaufgelöste Messungen analysiert. Einzelne Stickstoff-Fehlstellen-Zentren in Nanodiamanten werden in einem zweiten Themenkomplex als Einzelphotonenquellen eigesetzt. Diese werden durch den Einsatz einer Nahfeld-Sonde auf Mikrokugel-Resonatoren aufgebracht, wodurch die Emission aufgrund der Ankopplung an die Flüstergalerie-Moden der Kugeln die typischen, scharfen Überhöhungen im Spektrum aufweist. Diese Methode lässt sich nicht nur verwenden, um zwei oder mehr Emitter an die selben Resonanzen einer Kugel zu koppeln. Es ist auch möglich, die Kugeln in einem Vorbereitungsschritt zu charakterisieren, und so kann insbesondere eine spektrale Übereinstimmung zwischen einer der Resonanzen und dem Emitter erreicht werden. Desweiterne wird demonstriert, wie durch die Kopplung an eine plasmonische Antenne aus Goldnanokugeln mittels AFM auch die Effizienz der Einzelphotonenquelle gesteigert werden kann.The topic of the dissertation presented here is the investigation of nanoscopic emitters and the possibilities to influence their fluorescence behavior by controlled coupling to photonic and plasmonic structures. NaYF4 nanocrystals codoped with ytterbium and erbium are investigated since they provide excellent properties in upconverting of low-energetic photons to photons with higher energy. The fluorescence light that is generated in this process of a small cluster of nanocrystals is investigated on its dependence on the excitation intensity. With the help of an atomic force microscope (AFM) a dependence of the spectral composition of the fluorescence light from single nanocrystals on their size ranging between a few to 50 nm is demonstrated. By selective manipulation with the AFM, individual nanocrystals are coupled to gold nanospheres and the mechanisms of the observed plasmonic amplification of the emission is analyzed with time-resolved measurements. Single nitrogen–vacancy centers in nanodiamonds are employed as single-photon sources in a second subject area. A near-field probe is employed to attach these single quantum systems to microspherical resonators, by which their emission features the typical peaks in the spectrum due to the coupling to the whispering gallery modes of the spheres. This method can not only be applied to couple two or more single-photon emitters to the very same modes of a microsphere, but the resonators themselves can be pre-characterized to match one of the modes with the emitter. Furthermore, it will be demonstrated how the efficiency of a single-photon source can be enhanced by coupling the nitrogen-vacancy center to a plasmonic antenna made of gold nanospheres
In Situ Observation of Plasmon Tuning in a Single Gold Nanoparticle during Controlled Melting
In this Letter we study the relations
among shape, symmetry, and
plasmon resonance shift in a single gold nanoparticle during laser
melting. A beam of an argon ion laser is focused on a selected particle,
while its optical and shape properties can be observed with the help
of a combined dark-field/photoluminescence microscope and an atomic
force microscope, respectively. Starting from a spherical shape, radiation
pressure forms the melting gold particle into an upright standing
rod on a glass substrate, showing a characteristic dipole scattering
pattern. A red-shift of the photoluminescence signal and the scattering
spectrum is observed. The melting process can be controlled allowing
the formation of different particle heights and plasmon resonance
shifts. In situ tuning of the plasmon resonance of individual particles
is possible with this reversible melting process
An X-ray free-electron laser with a highly configurable undulator and integrated chicanes for tailored pulse properties
Abstract X-ray free-electron lasers (FELs) are state-of-the-art scientific tools capable to study matter on the scale of atomic processes. Since the initial operation of X-ray FELs more than a decade ago, several facilities with upgraded performance have been put in operation. Here we present the first lasing results of Athos, the soft X-ray FEL beamline of SwissFEL at the Paul Scherrer Institute in Switzerland. Athos features an undulator layout based on short APPLE-X modules providing full polarisation control, interleaved with small magnetic chicanes. This versatile configuration allows for many operational modes, giving control over many FEL properties. We show, for example, a 35% reduction of the required undulator length to achieve FEL saturation with respect to standard undulator configurations. We also demonstrate the generation of more powerful pulses than the ones obtained in typical undulators. Athos represents a fundamental step forward in the design of FEL facilities, creating opportunities in FEL-based sciences
Mutations of R882 change flanking sequence preferences of the DNA methyltransferase DNMT3A and cellular methylation patterns
DNMT3A mutations promote anthracycline resistance in acute myeloid leukemia via impaired nucleosome remodeling
Although the majority of acute myeloid leukemia (AML) patients initially respond to chemotherapy, many patients subsequently relapse; the mechanistic basis for AML persistence following chemotherapy has not been delineated. Recurrent somatic mutations in DNA methyltransferase 3A (DNMT3A), most frequently at arginine 882 (DNMT3A(mut)), are observed in AML(1–3) and in individuals with clonal hematopoiesis in the absence of leukemic transformation(4,5). DNMT3A(mut) AML patients have an inferior outcome when treated with standard-dose daunorubicin-based induction chemotherapy(6,7), suggesting that DNMT3A(mut) cells persist and drive relapse(8). Here we show that Dnmt3a(mut) induces hematopoietic stem cell (HSC) expansion, cooperates with Flt3(ITD) and Npm1(c) to induce AML in vivo, and promotes resistance to anthracycline chemotherapy. In AML patients, DNMT3A(R882) mutations predict for minimal residual disease (MRD), underscoring their role in AML chemoresistance. DNMT3A(mut) cells show impaired nucleosome eviction and chromatin remodeling in response to anthracyclines, resulting from attenuated recruitment of histone chaperone SPT-16 following anthracycline exposure. This defect leads to an inability to sense and repair DNA torsional stress, which results in increased mutagenesis. Our studies identify a critical role for DNMT3A(R882) mutations in driving AML chemoresistance, and highlight the importance of chromatin remodeling in response to cytotoxic chemotherapy