1,721,110 research outputs found
Dexamethasone modulation of LPS, IL-1, and TNF stimulated serum amyloid A synthesis in mice
No full text: Three secretory products of the macrophage, interleukin 1 (IL-1), tumor necrosis factor/cachectin (TNF) and hepatocyte stimulating factor/interleukin 6 (IL-6) modulate liver protein synthesis during the acute phase response. Induction of serum amyloid A (SAA) synthesis is one of the most notable acute phase changes in liver proteins, with maximal SAA concentrations varying over a thousand-fold range in proportion to the amount of tissue injury and cell necrosis. Exogenous IL-1 and TNF induce SAA synthesis in vivo and in vitro, while exogenous IL-6 is a far less potent stimulus of in vivo SAA gene expression. Dexamethasone (DEX), a potent inhibitor of macrophage IL-1, TNF and IL-6 synthesis, was utilized to analyze the endogenous mediators of SAA synthesis in mice injected with lipopolysaccharide (LPS). DEX, although itself exhibiting the capacity to stimulate SAA synthesis to a limited extent, significantly reduced LPS induced SAA production. However, DEX did not reduce, but rather potentiated, IL-1 and TNF stimulated SAA production, indicating that these monokines do not require macrophage products to mediate their in vivo SAA inducer activity. SAA synthesis was observed in adrenalectomized mice, following administration of LPS, IL-1 and TNF, indicating that SAA induction by monokines is not secondary to corticosteroid release
Scalable and efficient source of entangled frequency bins
No full textWe present a scalable and efficient approach for the generation of frequency-bin encoded qudit states in photonic integrated devices. We exploit a series of coherently pumped resonators, each generating photon pairs in specific frequency bins via spontaneous four-wave mixing. The generated state can be described as a coherent superposition of the states that would describe the pairs generated in each ring separately. As the frequency bin separation is not fixed by the resonator free spectral range, small resonators having large finesse and pair generation rates can be used
Resonant and nonresonant integrated third-order parametric down-conversion
No full textThird-order parametric down-conversion describes a class of nonlinear processes in which a pump photon can be down-converted into triplets of photons. It has been identified as a source of nonclassical light, with capabilities beyond those offered by better-established processes such as spontaneous four-wave mixing. Here we discuss the implementation of third-order parameter down-conversion (TOPDC) in integrated photonic systems. We derive equations for the rates of TOPDC in a nonresonant (waveguide) and resonant (microring) platform, such that the scaling with experimental parameters can be plainly seen. We find that generally nonresonant platforms should be pursued for spontaneous TOPDC (SpTOPDC), whereas resonant platforms are more suitable for stimulated TOPDC (StTOPDC). We present a sample calculation for TOPDC rates in sample systems with conservative and accessible parameters. We find that StTOPDC should be observable with the current fabrication technology, and that with some progress in the design of TOPDC platforms, integrated SpTOPDC too could be demonstrated in the near term
Integrated photonic sources of frequency-bin-encoded multipartite entangled states
No full textWe demonstrate that genuine multipartite entangled states can be generated using frequency bin encoding in integrated photonic platforms. We introduce a source of four-photon GHZ states and a source of three-photon W states. We predict generation rates on the order of 104 Hz for a silicon microring source with milliwatt pump powers. These results, along with the versatility and scalability of integrated structures, identify this as a promising approach for the generation of higher-dimensional and larger entangled states
Generation of photon pairs by stimulated emission in ring resonators
No full textThird-order parametric downconversion (TOPDC) describes a class of nonlinear interactions in which a pump photon is converted into a photon triplet. This process can occur spontaneously or it can be stimulated by seeding fields. Here we show that stimulated TOPDC (StTOPDC) can be exploited for the generation of quantum correlated photon pairs. We model StTOPDC in a microring resonator, predicting observable pair generation rates in a microring engineered for third-harmonic generation, and we examine the peculiar features of this approach when compared with second-order spontaneous parametric downconversion and spontaneous four-wave mixing. We conclude that if the experimental difficulties associated with implementing StTOPDC can be overcome, it may soon be possible to demonstrate this process in resonant integrated devices
Quantum frequency conversion and strong coupling of photonic modes using four-wave mixing in integrated microresonators
No full textGeneration of hyper-entangled states in strongly coupled topological defects
No full textWe investigate spontaneous parametric downconversion (SPDC) in a waveguide array supporting two strongly coupled topological guided modes. We show that it is possible to generate photon pairs that are hyper-entangled in energy and path. We study the state robustness against positional disorder of the waveguides, in terms of Schmidt number (SN), fidelity, and density matrix. We show that quantum correlations are in general robust due to the peculiar interplay between structure topology and second-order nonlinear interaction
No free lunch: The trade-off between heralding rate and efficiency in microresonator-based heralded single photon sources
Full text linkTwo strategies for modeling nonlinear optics in lossy integrated photonic structures
Full text linkWe present two complementary strategies for modeling nonlinear quantum optics
in realistic integrated optical devices, where scattering loss is present. In
the first strategy, we model scattering loss as an attenuation; in the second,
we employ a Hamiltonian treatment that includes a mechanism for scattering
loss, such as a `phantom waveguide.' These strategies can be applied to a broad
range of structures and processes. As an example, we use these two approaches
to model spontaneous four-wave mixing in (i) a ring-channel system and (ii) an
add-drop system. Even for these well-understood systems, our strategies yield
some novel results. We show the rates of photon pairs, broken pairs, and lost
pairs and their dependence on system parameters. We show that the properties of
lost and broken photon pairs in such structures can be related to those of the
un-scattered photon pairs, which are relatively simple to measure
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