Cooling a micro-mechanical resonator by quantum back-action from a noisy qubit

We study the role of qubit dephasing in cooling a mechanical resonator by quantum back-action. With a superconducting flux qubit as a specific example, we show that ground-state cooling of a mechanical resonator can only be realized if the qubit dephasing rate is sufficiently low.Comment: 5 pages, 3 figure

Effects of hadronic loops on the direct CP violation of BcB_{c}

It is well known that the final state interaction plays an important role in the decays of $B$-meson. The contribution of the final state interaction which is supposed to be long-distance effects, to the concerned processes can interfere with that of the short-distance effects produced via the tree and/or loop diagrams at quark-gluon level. The interference may provide a source for the direct CP violation $\mathcal{A}_{CP}$ in the process $B_{c}^{+}\to D^{0}\pi^{+}$. We find that a typical value of $\mathcal{A}_{CP}$ when the final state interaction effect is taken into account can be about -22% which is different from that without the final state interaction effect. Therefore, when we extract information on CP violation from the data which will be available at LHCb and the new experiments in $B$-factories, the contribution from the final state interaction must be included. This study may be crucial for searching new physics in the future.Comment: 15 pages, 3 figures, 2 tables. More discussion adde

Cavity QED treatment of scattering-induced efficient free-space excitation and collection in high-Q whispering-gallery microcavities

Whispering-gallery microcavity laser possesses ultralow threshold, whereas convenient free-space optical excitation and collection suffer from low efficiencies due to its rotational symmetry. Here we analytically study a three-dimensional microsphere coupled to a nano-sized scatterer in the framework of quantum optics. It is found that the scatterer is capable of coupling light in and out of the whispering-gallery modes (WGMs) without seriously degrading their high-Q properties, while the microsphere itself plays the role of a lens to focus the input beam on the scatterer and vice versa. Our analytical results show that (1) the high-Q WGMs can be excited in free space, and (2) over 50% of the microcavity laser emission can be collected within less than ${1}^{\circ}$. This coupling system holds great potential for low threshold microlasers free of external couplers.Comment: 10 pages, 8 figure

Inhibition of release of vasoactive and inflammatory mediators in airway and vascular tissues and macrophages by a Chinese herbal medicine formula for allergic rhinitis

Herbal therapies are being used increasingly for the treatment of allergic rhinitis. The aim of this study was to investigate the possible pharmacological actions and cellular targets of a Chinese herbal formula (RCM-101), which was previously shown to be effective in reducing seasonal allergic rhinitis symptoms in a randomized, placebo-controlled clinical trial. Rat and guinea pig isolated tissues (trachea and aorta) were used to study the effects of RCM-101 on responses to various mediators. Production of leukotriene 134 in porcine neutrophils and of prostaglandin E-2 and nitric oxide (NO) in Raw 264.7 cells were also measured. In rat and guinea pig tracheal preparations, RCM-101 inhibited contractile responses to compound 48/80 but not those to histamine (guinea pig preparations) or serotonin (rat preparations). Contractile responses of guinea pig tracheal preparations to carbachol and leukotriene C-4. and relaxant responses to substance P and prostaglandin E2 were not affected by RCM-101. In rat aortic preparations, precontracted with phenylephrine, endothelium-dependent relaxant responses to acetylcholine and endothelium-independent relaxant responses to sodium nitroprusside were not affected by RCM-101. However, RCM-101 inhibited relaxations to L-arginine in endothelium-denuded rat aortic preparations, which had been pre-incubated with lipopolysaccharide. RCM-101 did not affect leukotriene 134 formation in isolated porcine neutrophils, induced by the calcium ionophore A23187; however, it inhibited prostaglandin E-2 and NO production in lipopolysaccharide-stimulated murine macrophages (Raw 264.7 cells). The findings indicate that RCM-101 may have multiple inhibitory actions on the release and/or synthesis of inflammatory mediators involved in allergic rhinitis