1,709 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
Vegetation and peat characteristics of restiad bogs on Chatham Island (Rekohu), New Zealand
Restiad bogs dominated by Sporadanthus traversii on Chatham Island, New Zealand, were sampled to correlate vegetation patterns and peat properties, and to compare with restiad systems dominated by Sporadanthus ferrugineus and Empodisma minus in the Waikato region, North Island, New Zealand. Classification and ordination resulted in five groups that reflected a disturbance gradient. The largest S. traversii group, which comprised plots from central, relatively intact bogs, had the lowest levels of total nitrogen (mean 1.20 mg cm-3), total phosphorus (mean 0.057 mg cm-3), total potassium (mean 0.083 mg cm-3), and available phosphorus (mean 18.6 ÎŒg cm-3). Modification by drainage, stock, and fires resulted in a decline of S. traversii and an increase of Gleichenia dicarpa fern cover, together with elevated peat nutrient levels and higher bulk density. Compared with peat dominated by Sporadanthus ferrugineus or Empodisma minus in relatively unmodified Waikato restiad bogs, Chatham Island peat under S. traversii has significantly higher total potassium, total nitrogen, available phosphorus, bulk density, and von Post decomposition indices, and significantly lower pH. Sporadanthus traversii and Empodisma minus have similar ecological roles in restiad bog development, occupying a relatively wide nutrient range, and regenerating readily from seed after fire. Despite differences in root morphology, S. traversii and E. minus are the major peat formers in raised restiad bogs on Chatham Island and in Waikato, respectively, and could be regarded as ecological equivalents
Primary breast cancer stem-like cells metastasise to bone, switch phenotype and acquire a bone tropism signature
Towards mirror symmetry \`a la SYZ for generalized Calabi-Yau manifolds
Fibrations of flux backgrounds by supersymmetric cycles are investigated. For
an internal six-manifold M with static SU(2) structure and mirror \hat{M}, it
is argued that the product M x \hat{M} is doubly fibered by supersymmetric
three-tori, with both sets of fibers transverse to M and \hat{M}. The mirror
map is then realized by T-dualizing the fibers. Mirror-symmetric properties of
the fluxes, both geometric and non-geometric, are shown to agree with previous
conjectures based on the requirement of mirror symmetry for Killing
prepotentials. The fibers are conjectured to be destabilized by fluxes on
generic SU(3)xSU(3) backgrounds, though they may survive at type-jumping
points. T-dualizing the surviving fibers ensures the exchange of pure spinors
under mirror symmetry.Comment: 30 pages, 3 figures, LaTeX; v2: references adde
D-branes in Generalized Geometry and Dirac-Born-Infeld Action
The purpose of this paper is to formulate the Dirac-Born-Infeld (DBI) action
in a framework of generalized geometry and clarify its symmetry. A D-brane is
defined as a Dirac structure where scalar fields and gauge field are treated on
an equal footing in a static gauge. We derive generalized Lie derivatives
corresponding to the diffeomorphism and B-field gauge transformations and show
that the DBI action is invariant under non-linearly realized symmetries for all
types of diffeomorphisms and B-field gauge transformations. Consequently, we
can interpret not only the scalar field but also the gauge field on the D-brane
as the generalized Nambu-Goldstone boson.Comment: 32 pages, 4 figures, ver2:typos corrected, references adde
Self-consistent treatment of the self-energy in nuclear matter
The influence of hole-hole propagation in addition to the conventional
particle-particle propagation, on the energy per nucleon and the momentum
distribution is investigated. The results are compared to the
Brueckner-Hartree-Fock (BHF) calculations with a continuous choice and
conventional choice for the single-particle spectrum. The Bethe-Goldstone
equation has been solved using realistic interactions. Also, the structure
of nucleon self-energy in nuclear matter is evaluated. All the self-energies
are calculated self-consistently. Starting from the BHF approximation without
the usual angle-average approximation, the effects of hole-hole contributions
and a self-consistent treatment within the framework of the Green function
approach are investigated. Using the self-consistent self-energy, the hole and
particle self-consistent spectral functions including the particle-particle and
hole-hole ladder contributions in nuclear matter are calculated using realistic
interactions. We found that, the difference in binding energy between both
results, i.e. BHF and self-consistent Green function, is not large. This
explains why is the BHF ignored the 2h1p contribution.Comment: Preprint 20 pages including 15 figures and one tabl
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
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