Entanglement-assisted transformation is asymptotically equivalent to multiple-copy transformation

We show that two ways of manipulation of quantum entanglement, namely, entanglement-assisted local transformation [D. Jonathan and M. B. Plenio, Phys. Rev. Lett. {\bf 83}, 3566 (1999)] and multiple-copy transformation [S. Bandyopadhyay, V. Roychowdhury, and U. Sen, Phys. Rev. A {\bf 65}, 052315 (2002)], are equivalent in the sense that they can asymptotically simulate each other's ability to implement a desired transformation from a given source state to another given target state with the same optimal success probability. As a consequence, this yields a feasible method to evaluate the optimal conversion probability of an entanglement-assisted transformation.Comment: 5 pages, revtex4, references updated, no figures. A slightly shorter version appears in PR

Implementation of packaged integrated antenna with embedded front end for Bluetooth applications

The design, integration and realization of system in enhanced package approach towards fully functional system level integration by using a compact Bluetooth USB dongle as the demonstrator is presented here. The integration was done on FR4 substrates, which is totally compatible with today’s printed circuit board manufacturing capability. A commercially available Bluetooth integrated chip was chosen as the chipset of our demonstrator, and a package integrated antenna together with an embedded front end completes the system in package integration. The front end developed here is based on an embedded meander line combline filter and an embedded transformer balun. The filter has a 35% area reduction when compared with the classical combline filter and similar performance. The balun has the coils distributed on three layers that minimized the board area needed it and optimizes the performances. The proposed packaged integrated antenna approach is successfully demonstrated here and the new module shows excellent performance when compared with a commercial solution, surpassing the normal Bluetooth class II dongle range which is up to 10 m and increasing the module range up to 120 m without an extra power amplifier

Annihilation Type Radiative Decays of BB Meson in Perturbative QCD Approach

With the perturbative QCD approach based on $k_T$ factorization, we study the pure annihilation type radiative decays $B^0 \to \phi\gamma$ and $B^0\to J/\psi \gamma$. We find that the branching ratio of $B^0 \to \phi\gamma$ is $(2.7^{+0.3+1.2}_{-0.6-0.6})\times10^{-11}$, which is too small to be measured in the current $B$ factories of BaBar and Belle. The branching ratio of $B^0\to J/\psi \gamma$ is $({4.5^{+0.6+0.7}_{-0.5-0.6}})\times10^{-7}$, which is just at the corner of being observable in the $B$ factories. A larger branching ratio $BR(B_s^0 \to J/\psi \gamma) \simeq 5 \times 10^{-6}$ is also predicted. These decay modes will help us testing the standard model and searching for new physics signals.Comment: 4 pages, revtex, with 1 eps figur

On the spectrum of operators concerned with the reduced singular Cauchy integral

We investigate spectrums of the reduced singular Cauchy operator and its real and imaginary components

The Catalytic and Non-catalytic Functions of the Brahma Chromatin-Remodeling Protein Collaborate to Fine-Tune Circadian Transcription in Drosophila.

Daily rhythms in gene expression play a critical role in the progression of circadian clocks, and are under regulation by transcription factor binding, histone modifications, RNA polymerase II (RNAPII) recruitment and elongation, and post-transcriptional mechanisms. Although previous studies have shown that clock-controlled genes exhibit rhythmic chromatin modifications, less is known about the functions performed by chromatin remodelers in animal clockwork. Here we have identified the Brahma (Brm) complex as a regulator of the Drosophila clock. In Drosophila, CLOCK (CLK) is the master transcriptional activator driving cyclical gene expression by participating in an auto-inhibitory feedback loop that involves stimulating the expression of the main negative regulators, period (per) and timeless (tim). BRM functions catalytically to increase nucleosome density at the promoters of per and tim, creating an overall restrictive chromatin landscape to limit transcriptional output during the active phase of cycling gene expression. In addition, the non-catalytic function of BRM regulates the level and binding of CLK to target promoters and maintains transient RNAPII stalling at the per promoter, likely by recruiting repressive and pausing factors. By disentangling its catalytic versus non-catalytic functions at the promoters of CLK target genes, we uncovered a multi-leveled mechanism in which BRM fine-tunes circadian transcription

Multipartite unlockable bound entanglement in the stabilizer formalism

We find an interesting relationship between multipartite bound entangled states and the stabilizer formalism. We prove that if a set of commuting operators from the generalized Pauli group on $n$ qudits satisfy certain constraints, then the maximally mixed state over the subspace stabilized by them is an unlockable bound entangled state. Moreover, the properties of this state, such as symmetry under permutations of parties, undistillability and unlockability, can be easily explained from the stabilizer formalism without tedious calculation. In particular, the four-qubit Smolin state and its recent generalization to even number of qubits can be viewed as special examples of our results. Finally, we extend our results to arbitrary multipartite systems in which the dimensions of all parties may be different.Comment: 7 pages, no figur

Equilibrium shape and dislocation nucleation in strained epitaxial nanoislands

We study numerically the equilibrium shapes, shape transitions and dislocation nucleation of small strained epitaxial islands with a two-dimensional atomistic model, using simple interatomic pair potentials. We first map out the phase diagram for the equilibrium island shapes as a function of island size (up to N = 105 atoms) and lattice misfit with the substrate and show that nanoscopic islands have four generic equilibrium shapes, in contrast with predictions from the continuum theory of elasticity. For increasing substrate-adsorbate attraction, we find islands that form on top of a finite wetting layer as observed in Stranski-Krastanow growth. We also investigate energy barriers and transition paths for transitions between different shapes of the islands and for dislocation nucleation in initially coherent islands. In particular, we find that dislocations nucleate spontaneously at the edges of the adsorbate-substrate interface above a critical size or lattice misfit.Comment: 4 pages, 3 figures, uses wrapfig.sty and epsfig.st

Using dark modes for high-fidelity optomechanical quantum state transfer

In a recent publication [Y.D. Wang and A.A. Clerk, Phys. Rev. Lett. 108, 153603 (2012)], we demonstrated that one can use interference to significantly increase the fidelity of state transfer between two electromagnetic cavities coupled to a common mechanical resonator over a naive sequential-transfer scheme based on two swap operations. This involved making use of a delocalized electromagnetic mode which is decoupled from the mechanical resonator, a so-called "mechanically-dark" mode. Here, we demonstrate the existence of a new "hybrid" state transfer scheme which incorporates the best elements of the dark-mode scheme (protection against mechanical dissipation) and the double-swap scheme (fast operation time). Importantly, this new scheme also does not require the mechanical resonator to be prepared initially in its ground state. We also provide additional details on the previously-described interference-enhanced transfer schemes, and provide an enhanced discussion of how the interference physics here is intimately related to the optomechanical analogue of electromagnetically-induced transparency (EIT). We also compare the various transfer schemes over a wide range of relevant experimental parameters, producing a "phase diagram" showing the the optimal transfer scheme for different points in parameter space.Comment: 39 pages, 11 figures NJP 14 (Focus issue on Optomechanics

Solving the Dirac equation with nonlocal potential by Imaginary Time Step method

The Imaginary Time Step (ITS) method is applied to solve the Dirac equation with the nonlocal potential in coordinate space by the ITS evolution for the corresponding Schr\"odinger-like equation for the upper component. It is demonstrated that the ITS evolution can be equivalently performed for the Schr\"odinger-like equation with or without localization. The latter algorithm is recommended in the application for the reason of simplicity and efficiency. The feasibility and reliability of this algorithm are also illustrated by taking the nucleus $^{16}$O as an example, where the same results as the shooting method for the Dirac equation with localized effective potentials are obtained