158 research outputs found
Narrow optical linewidths and spin pumping on charge-tunable close-to-surface self-assembled quantum dots in an ultrathin diode
We demonstrate full charge control, narrow optical linewidths, and optical spin pumping on single self-assembled InGaAs quantum dots embedded in a 162.5ânm-thin diode structure. The quantum dots are just 88nm from the top GaAs surface. We design and realize a pâiânâiân diode that allows single-electron charging of the quantum dots at close-to-zero applied bias. In operation, the current flow through the device is extremely small resulting in low noise. In resonance fluorescence, we measure optical linewidths below 2ÎźeV, just a factor of 2 above the transform limit. Clear optical spin pumping is observed in a magnetic field of 0.5T in the Faraday geometry. We present this design as ideal for securing the advantages of self-assembled quantum dotsâhighly coherent single-photon generation, ultrafast optical spin manipulationâin the thin diodes required in quantum nanophotonics and nanophononics applications
Indistinguishable and efficient single photons from a quantum dot in a planar nanobeam waveguide
We demonstrate a high-purity source of indistinguishable single photons using a quantum dot embedded in a nanophotonic waveguide. The source features a near-unity internal coupling efficiency and the collected photons are efficiently coupled off chip by implementing a taper that adiabatically couples the photons to an optical fiber. By quasiresonant excitation of the quantum dot, we measure a single-photon purity larger than 99.4% and a photon indistinguishability of up to 94Âą1% by using p-shell excitation combined with spectral filtering to reduce photon jitter. A temperature-dependent study allows pinpointing the residual decoherence processes, notably the effect of phonon broadening. Strict resonant excitation is implemented as well as another means of suppressing photon jitter, and the additional complexity of suppressing the excitation laser source is addressed. The paper opens a clear pathway towards the long-standing goal of a fully deterministic source of indistinguishable photons, which is integrated on a planar photonic chip
Lifetimes and Quantum Efficiencies of Quantum Dots Deterministically Positioned in Photonic-Crystal Waveguides
Interfacing single emitters and photonic nanostructures enables modifying
their emission properties, such as enhancing individual decay rates or
controlling the emission direction. To achieve full control, the single emitter
must be positioned in the nanostructures deterministically. Here, we use
spectroscopy to gain spectral and spatial information about individual quantum
dots in order to position each emitter in a pre-determined location in a unit
cell of a photonic-crystal waveguide. Depending on the spatial and spectral
positioning within the structured nanophotonic mode, we observe that the
quantum dot emission can either be suppressed or enhanced. These results
demonstrate the capacity of photonic-crystal waveguides to control the emission
of single photons and that the ability to position quantum dots will be crucial
to the creation of complex multi-emitter quantum photonic circuits.Comment: 7 pages, 7 figure
On-Chip Nanomechanical Filtering of Quantum-Dot Single-Photon Sources
Semiconductor quantum dots in photonic integrated circuits enable scaling
quantum-information processing to many single photons and quantum-optical
gates. On-chip spectral filters are essential to achieve high-purity and
coherent photon emission from quantum dots embedded in waveguides, without
resorting to free-space optics. Such spectral filters should be tunable, to
compensate for the inhomogeneous spectral distribution of the quantum dots
transitions. Here, we report an on-chip filter monolithically integrated with
quantum dots, that uses nanomechanical motion for tuning its resonant
wavelength over 10 nm, enabling operation at cryogenic temperatures and
avoiding cross-talk with the emitter. We demonstrate single-photon emission
from a quantum dot under non-resonant excitation by employing only the on-chip
filter. These results are key for the development of fully-integrated
de-multiplexing, multi-path photon encoding schemes, and multi-emitter
circuits
Integrated Whispering-Gallery-Mode Resonator for Solid-State Coherent Quantum Photonics
Tailored photonic cavities allow enhancing light-matter interaction
ultimately to create a fully coherent quantum interface. Here, we report on an
integrated microdisk cavity containing self-assembled quantum dots to
coherently route photons between different access waveguides. We measure a
Purcell factor of for a cavity quality factor of about
10,000, allowing us to observe clear signatures of coherent scattering of
photons by the quantum dots. We show how this integrated system can coherently
re-route photons between the drop and bus ports, and how this routing is
controlled by detuning the quantum dot and resonator, or through the strength
of the excitation beam, where a critical photon number less than one photon per
lifetime is required. We discuss the strengths and limitations of this
approach, focusing on how the coherent scattering and single-photon
nonlinearity can be used to increase the efficiency of quantum devices such as
routers or Bell-state analyzers
A Charge-Tunable Quantum Dot Deep in The Strong Coupling Regime of Cavity QED
International audienceWe present high-cooperativity (C up to 140) strong coupling of a charge-tunable InAs quantum dot embedded in a tunable Fabry-PĂŠrot microcavity (Q=500,000). Via second-order correlation measurements we show high single-photon purity in the photon-blockade regime and pronounced vacuum Rabi oscillations in the photon-induced tunneling regime
Coherent Optical Control of a Quantum-Dot Spin-Qubit in a Waveguide-Based Spin-Photon Interface
Waveguide-based spin-photon interfaces on the GaAs platform have emerged as a promising system for a variety of quantum information applications directly integrated into planar photonic circuits. The coherent control of spin states in a quantum dot can be achieved by applying circularly polarized laser pulses that may be coupled into the planar waveguide vertically through radiation modes. However, proper control of the laser polarization is challenging since the polarization is modified through the transformation from the far field to the exact position of the quantum dot in the nanostructure. Here, we demonstrate polarization-controlled excitation of a quantum-dot electron spin and use that to perform coherent control in a Ramsey interferometry experiment. The Ramsey interference reveals an inhomogeneous dephasing time of 2.2 +/- 0.1 ns, which is comparable to the values so far only obtained in bulk media. We analyze the experimental limitations in spin initialization fidelity and Ramsey contrast and identify the underlying mechanisms
11q13 is a susceptibility locus for hormone receptor positive breast cancer.
Journal articleA recent two-stage genome-wide association study (GWAS) identified five novel breast cancer susceptibility loci on chromosomes 9, 10, and 11. To provide more reliable estimates of the relative risk associated with these loci and investigate possible heterogeneity by subtype of breast cancer, we genotyped the variants rs2380205, rs1011970, rs704010, rs614367, and rs10995190 in 39 studies from the Breast Cancer Association Consortium (BCAC), involving 49,608 cases and 48,772 controls of predominantly European ancestry. Four of the variants showed clear evidence of association (P â ¤ 3 à 10(-9) ) and weak evidence was observed for rs2380205 (P = 0.06). The strongest evidence was obtained for rs614367, located on 11q13 (per-allele odds ratio 1.21, P = 4 à 10(-39) ). The association for rs614367 was specific to estrogen receptor (ER)-positive disease and strongest for ER plus progesterone receptor (PR)-positive breast cancer, whereas the associations for the other three loci did not differ by tumor subtype.EC Seventh Framework Programme - grant number HEALTH-F2-2009-223175peer-reviewe
Search for narrow resonances using the dijet mass spectrum in pp collisions at sâ=8ââTeV
Results are presented of a search for the production of new particles decaying to pairs of partons (quarks, antiquarks, or gluons), in the dijet mass spectrum in proton-proton collisions at sâ=8ââTeV. The data sample corresponds to an integrated luminosity of 4.0ââfbâ1, collected with the CMS detector at the LHC in 2012. No significant evidence for narrow resonance production is observed. Upper limits are set at the 95% confidence level on the production cross section of hypothetical new particles decaying to quark-quark, quark-gluon, or gluon-gluon final states. These limits are then translated into lower limits on the masses of new resonances in specific scenarios of physics beyond the standard model. The limits reach up to 4.8 TeV, depending on the model, and extend previous exclusions from similar searches performed at lower collision energies. For the first time mass limits are set for the RandallâSundrum graviton model in the dijet channel
- âŚ