Bright sources of indistinguishable single photons are strongly needed for the scalability of quantum information processing. Semiconductor quantum dots are promising systems to build such sources. Several works demonstrated emission of indistinguishable photons while others proposed various approaches to efficiently collect them. Here we combine both properties and report on the fabrication of ultrabright sources of indistinguishable single photons, thanks to deterministic positioning of single quantum dots in well-designed pillar cavities. Brightness as high as 0.79±0.08 collected photon per pulse is demonstrated. The indistinguishability of the photons is investigated as a function of the source brightness and the excitation conditions. We show that a two-laser excitation scheme allows reducing the fluctuations of the quantum dot electrostatic environment under high pumping conditions. With this method, we obtain 82 ± 10% indistinguishability for a brightness as large as 0.65 ± 0.06 collected photon per pulse.

The scalability of a quantum network based on semiconductor quantum dots lies in the possibility of having an electrical control of the quantum dot state as well as controlling its spontaneous emission. The technological challenge is then to define electrical contacts on photonic microstructures optimally coupled to a single quantum emitter. Here we present a novel photonic structure and a technology allowing the deterministic implementation of electrical control for a quantum dot in a microcavity. The device consists of a micropillar connected to a planar cavity through one-dimensional wires; confined optical modes are evidenced with quality factors as high as 33,000. We develop an advanced in-situ lithography technique and demonstrate the deterministic spatial and spectral coupling of a single quantum dot to the connected pillar cavity. Combining this cavity design and technology with a diode structure, we demonstrate a deterministic and electrically tunable single-photon source with an extraction efficiency of around 53±9%.

In just 20 years of history, the field of optomechanics has achieved impressive progress, stepping into the quantum regime just 5 years ago. Such remarkable advance relies on the technological revolution of nano-optomechanical systems, whose sensitivity towards thermal decoherence is strongly limited due to their ultra-low mass. Here we report a hybrid approach pushing nano-optomechanics to even lower scales. The concept relies on synthesising an efficient optical scatterer at the tip of singly clamped carbon nanotube resonators. We demonstrate high signal-to-noise motion readout and record force sensitivity, two orders of magnitude below the state of the art. Our work opens the perspective to extend quantum experiments and applications at room temperature.

The paper reports a new route for the fabrication and determination of physicochemical properties and biological activity, of metallic silica-based nanostructure (Ag/SiO2, Cu/SiO2).

Drug-resistance of bacteria is an ongoing problem in hospital treatment. The main mechanism of bacterial virulency in human infections is based on their adhesion ability and biofilm formation. Many approaches have been invented to overcome this problem, i.e. treatment with antibacterial biomolecules, which have some limitations e.g. enzymatic degradation and short shelf stability. Silver nanoparticles (AgNPs) may be alternative to these strategies due to their unique and high antibacterial properties. Herein, we report on yeast Saccharomyces cerevisiae extracellular-based synthesis of AgNPs. Transmission electron microscopy (TEM) revealed the morphology and structure of the metallic nanoparticles, which showed a uniform distribution and good colloid stability, measured by hydrodynamic light scattering (DLS). The energy dispersive X-ray spectroscopy (EDS) of NPs confirms the presence of silver and showed that sulfur-rich compounds act as a capping agent being adsorbed on the surface of AgNPs. Antimicrobial tests showed that AgNPs inhibit the bacteria growth, while have no impact on fungi growth. Moreover, tested NPs was characterized by high inhibitory potential of bacteria biofilm formation but also eradication of established biofilms. The cytotoxic effect of the NPs on four mammalian normal and cancer cell lines was tested through the metabolic activity, cell viability and wound-healing assays. Last, but not least, ability to deep penetration of the silver colloid to the root canal was imaged by scanning electron microscopy (SEM) to show its potential as the material for root-end filling.

Ultrafast lattice dynamics of few quintuple layers of topological insulator (TI) Bi2Te3 is studied with time-resolved optical pump-probe spectroscopy. Both optical and acoustic phonons are photogenerated and detected. Here, in order to get new insights on the out-of-equilibrium electron-phonon coupling and phonons dynamics in confined TI, different nanostructures have been investigated (single or polycrystalline QLs assemblies and nano-crystallized islands). Contrary to previous literature claims, we show that even for nanostructures containing only 10 quintuple layers (QLs), the symmetric A1g(I) coherent optical phonon is efficiently photogenerated and no restriction due to the structural confinement appears. We also observe that whatever the arrangement of the nanostructures, the A1g(I) optical phonon features are similar (lifetime). We also report the observation of confined coherent acoustic phonons propagating from QLs to QLs whose spectrum is, this time, very sensitive to the atomic arrangement. In the case of the single crystalline ultrathin film, the time of flight analysis of these acoustic phonons provides direct estimate of the elastic properties of these nanostructures as well as some estimates of Van der Waals interactions between QLs.

We present second-order photon correlation measurements on single InP/͑Ga,In͒P quantum dots as a function of temperature. Low background emission allows to obtain antibunching minima g ͑2͒ ͑0͒ below 0.25 up to 45 K. The antibunching time R increases or decreases with temperature depending on the quantum-dot size. The two trends result from a competition between hole thermal excitation and dark-to-bright exciton transitions. The former prevails in smaller dots showing increasing R with temperature, while the latter dominates in larger quantum dots showing decreasing R with temperature. DOI: 10.1103/PhysRevB.80.161305 PACS number͑s͒: 78.67.Hc, 78.55.Cr, 42.50.Ar Semiconductor quantum dots ͑QDs͒ are among the most promising single-photon emitters ͑SPEs͒ for quantum information applications due to their versatility, scalability, and ease to handle as compared to atom or ion-based SPEs. [1][2][3][4] However, the use of semiconductor QDs as true "on demand" SPEs is conditioned by the presence of "background photons" ͑photons emitted outside the QD but at the QD energy͒ and decoherence. 5 One important source of decoherence in QDs is the random transition between bright exciton ͑BX͒ and dark exciton ͑DX͒ states ͑exciton states with total angular momentum 1 and 2, respectively͒. 6 Exciton energy splittings, as the dark-bright exciton splitting E DB and the fine-structure splitting ⌬ FS , which are large in QDs as compared to higher dimensional systems due to the increased electron-hole Coulomb interaction, are strongly sensitive to the QD size and shape. 7-9 InP QDs have received special attention for their potential use as SPEs in the visible range. [10][11][12][13][14][15][16] Photon correlation measurements for both continuous 9,11 and pulsed excitation 11,13,15 as well as under electrical injection 14 show clear antibunching dips in the second-order photon correlation function g ͑2͒ ͑ ͒ at zero delay ͑ =0͒. The standard form of the correlation function iswhere R is the characteristic ͑minimum͒ time needed for the emission of a second photon after the first one has been emitted by the QD and ␤ is generally determined by background photons. A value ␤ = 1 indicates perfect SPE. The low values of g ͑2͒ ͑0͒ found in InP QDs ͑between 0.1 and 0.2͒ ͑Refs. 10-15͒ is indicative of efficient single-photon emission. High-temperature operation of a SPE is beneficial for practical uses. Antibunching dips up to 200 K have been reported for GaN ͑Ref. 17͒ and CdSe ͑Ref. 18͒ QDs and up to 90 K in InGaAs/AlGaAs QDs. 19 In InP QDs an upper limit of 80 K has been reached using Al containing barriers. 13 Upon raising temperature the g ͑2͒ ͑0͒ value progressively increases due to the increasing background luminescence. Temperature also influences the antibunching width. Indeed R depends on several factors, as the pumping rate, the exciton lifetime 20 and the carrier relaxation time, some of them being temperature dependent. An increase in R with temperature has been reported in InGaAs/AlGaAs QDs. 19 In this Rapid Communication we pres...

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.