707 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
Pulsating emission of droplets from an electrified meniscus.
A numerical description is given for the pulsating emission of droplets from an electrified meniscus of an inviscid liquid of infinite electrical conductivity which is injected at a constant flow rate into a region of uniform, continuous or time periodic, electric field. Under a continuous field, the meniscus attains a periodic regime in which bursts of tiny droplets are emitted from its tip. At low electric fields this regime consists of sequences of emission bursts interspersed with sequences of meniscus oscillations without droplet emission, while at higher fields the bursts occur periodically. These results are in qualitative agreement with experimental results in the literature. Under a time periodic electric field with square waveform, the electric stress that acts on the surface of the liquid while the field is on may generate a tip that emits tiny droplets or may accelerate part of the meniscus and lead to a second emission mode in which a few large droplets are emitted after the electric field is turned off. Conditions under which each emission mode or a combination of the two are realized are discussed for low frequency oscillatory fields. A simplified model is proposed for high electric field frequencies, of the order of the capillary frequency of the meniscus. This model allows computing the average emission rate as a function of the amplitude, duration and bias of the electric field square wave, and shows that droplet emission fails to follow the applied field above a certain frequenc
Superradiance from an ultrathin film of three-level V-type atoms: Interplay between splitting, quantum coherence and local-field effects
We carry out a theoretical study of the collective spontaneous emission
(superradiance) from an ultrathin film comprised of three-level atoms with
-configuration of the operating transitions. As the thickness of the system
is small compared to the emission wavelength inside the film, the local-field
correction to the averaged Maxwell field is relevant. We show that the
interplay between the low-frequency quantum coherence within the subspace of
the upper doublet states and the local-field correction may drastically affect
the branching ratio of the operating transitions. This effect may be used for
controlling the emission process by varying the doublet splitting and the
amount of low-frequency coherence.Comment: 15 pages, 5 figure
Optical control of spin textures in quasi-one-dimensional polariton condensates
We investigate, through polarization-resolved spectroscopy, the spin
transport by propagating polariton condensates in a quasi one-dimensional
microcavity ridge along macroscopic distances. Under circularly polarized,
continuous-wave, non-resonant excitation, a sinusoidal precession of the spin
in real space is observed, whose phase depends on the emission energy. The
experiments are compared with simulations of the spinor-polariton condensate
dynamics based on a generalized Gross-Pitaevskii equation, modified to account
for incoherent pumping, decay and energy relaxation within the condensate.Comment: 10 pages, 9 figure
Explosive seed dispersal depends on SPL7 to ensure sufficient copper for localized lignin deposition via laccases
Exploding seed pods evolved in the Arabidopsis relative Cardamine hirsuta via morphomechanical innovations that allow the storage and rapid release of elastic energy. Asymmetric lignin deposition within endocarpb cell walls is one such innovation that is required for explosive seed dispersal and evolved in association with the trait. However, the genetic control of this novel lignin pattern is unknown. Here, we identify three lignin-polymerizing laccases, LAC4, 11, and 17, that precisely colocalize with, and are redundantly required for, asymmetric lignification of endocarpb cells. By screening for C. hirsuta mutants with less lignified fruit valves, we found that loss of function of the transcription factor gene SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 7 (SPL7) caused a reduction in endocarpb cell-wall lignification and a consequent reduction in seed dispersal range. SPL7 is a conserved regulator of copper homeostasis and is both necessary and sufficient for copper to accumulate in the fruit. Laccases are copper-requiring enzymes. We discovered that laccase activity in endocarpb cell walls depends on the SPL7 pathway to acclimate to copper deficiency and provide sufficient copper for lignin polymerization. Hence, SPL7 links mineral nutrition to efficient dispersal of the next generation
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