Search

Reconfigurable Intelligent Surface (RIS) is a promising technology that may effectively improve the quality of signals in wireless communications. In practice, however, the ``double fading'' effect undermines the application of RIS and constitutes a significant challenge to its commercialization. To address this problem, we present a novel 2-bit programmable amplifying transmissive RIS with a power amplification function to enhance the transmission of electromagnetic signals. The transmissive function is achieved through a pair of radiation patches located on the upper and lower surfaces, respectively, while a microstrip line connects two patches. A power amplifier, SP4T switch, and directional coupler provide signal amplification and a 2-bit phase shift. To characterize the signal enhancement of active transmissive RIS, we propose a dual radar cross section (RCS)-based path loss model to predict the power of the received signal for active transmissive RIS-aided wireless communication systems. Simulation and experimental results verify the reliability of the RIS design, and the proposed path loss model is validated by measurements. Compared with the traditional passive RIS, the signal power gain in this design achieves 11.9 dB.

A novel intense beam-driven scheme for high yield of the tri-alpha reaction 11B(p,{\alpha})2{\alpha} was investigated. We used a foam target made of cellulose triacetate (TAC, C_9H_{16}O_8) doped with boron. It was then heated volumetrically by soft X-ray radiation from a laser heated hohlraum and turned into a homogenous, and long living plasma. We employed a picosecond laser pulse to generate a high-intensity energetic proton beam via the well-known Target Normal Sheath Acceleration (TNSA) mechanism. We observed up to 10^{10}/sr {\alpha} particles per laser shot. This constitutes presently the highest yield value normalized to the laser energy on target. The measured fusion yield per proton exceeds the classical expectation of beam-target reactions by up to four orders of magnitude under high proton intensities. This enhancement is attributed to the strong electric fields and nonequilibrium thermonuclear fusion reactions as a result of the new method. Our approach shows opportunities to pursue ignition of aneutronic fusion.

The reports of room-temperature superconductivity in Cu-doped Pb-apatite draw intense interests and debates. Herein, based on the density functional theory, we show that the Cu-insertion in Pb-apatite is thermodynamically stable and further carrier doping can convert the system CuPb$_{10}$(PO$_4$)$_6$O into metal. The electric conduction is mainly along the one-dimensional (1D) Cu-O chains in the c-axis (out-of-plane). The calculated conductance along the c-axis is larger than the in-plane ones by 2 magnitude orders, indicating the 1D conduction behavior. Moreover, the 1D Cu-O chain is an anti-ferromagnetic Mott insulator at zero-doping point due to the super-exchange. Further electron/hole-doping will erase the anti-ferromagnetism. Therefore, the Cu-inserted system CuPb$_{10}$(PO$_4$)$_6$O show transport and magnetic features similar to the cuprate superconductors. On the other hand, the O-insertion can also induce the metallic states, in which the conductance along the out-of-plane direction is higher than the in-plane direction by 6-folds. Our results display the metallization of Pb$_{10}$(PO$_4$)$_6$O via Cu/O-insertions, and suggesting the electric conductions along the c-axis might dominate the transport behaviors., Comment: 17 pages, 9 figures

Recently, much attention has been paid to uncovering the influence of dissipation on a quantum system, particularly on how the non-Hermitian (NH) terms modify the band topology of topological materials and reshape the profile of the wavefunctions of a system (or the NH skin effect). In this paper, a specific NH skin effect that induced by local dissipation is studied for chiral edge modes, in which the NH term corresponds to the local imaginary Fermi velocity of the chiral edge modes. By solving the NH Schr\"{o}dinger equation of the non-Hermitian chiral edge modes (nhCEs) with complex Fermi velocity, we uncovered the remarkable complex spectra and the wavefunctions of the nhCEs. We find that the complex spectra of these modes is a straight line in the topological materials, and its chirality can separates the modes with positive energy from those with negative energy, in which they are localized at different positions. We also studied the nhCEs at the boundary of 2-dimensional (2D) topological materials, the 2D $p$-wave superconductor and the Qi-Wu-Zhang model, in which the general law of nhCEs was verified. We expect that our findings will pave the way for researching the transport properties of the chiral edge modes in the non-equilibrium context., Comment: 7 pages, 6 figures

The decoherence effect caused by the coupling between the system and the environment undoubtedly leads to the errors in efficient implementations of two (or three) qubit logical gates in quantum information processing. Fortunately, decoherence-free subspace (DFS) introduced can effectively decrease the influence of decoherence effect. In this paper, we propose some schemes for setting up a family of quantum control gates, including controlled-NOT (CNOT), Toffoli, and Fredkin gates for two or three logical qubits by means of cross-Kerr nonlinearities in DFS. These three logical gates require neither complicated quantum computational circuits nor auxiliary photons (or entangled states). The success probabilities of three logical gates are approximate 1 by performing the corresponding classical feed-forward operations based on the different measuring results of the X-homodyne detectors, and their fidelities are robust against the photon loss with the current technology. The proposed logical gates rely on only simple linear-optics elements, available single-qubit operations, and mature measurement methods, making our proposed gates be feasible and efficient in practical applications., Comment: 17 pages, 16 figures

Laser-driven brilliant controllable polarized $\gamma$-photon sources open the way for designing compact $\gamma\gamma$ collider, which enable the large yield of linear Breit-Wheeler (LBW) pairs in a single shot and thus provide an opportunity for the investigation of polarized LBW process. In this work we investigate the polarization characteristics of LBW pair production via our developed spin-resolved binary collision simulation method. Polarization of $\gamma$-photons modifies the kinematics of scattering particles and induces the correlated energy-angle shift of LBW pairs, and the latter's polarization characteristic depends on the helicity configures of scattering particles. Our method confirms that the polarized $\gamma\gamma$ collider with an asymmetric setup can be performed with currently achievable laser facilities to produce abundant polarized LBW pairs, fulfilling the detection power of polarimetries. The precise knowledge of polarized LBW process is in favor of the calibration and monitor of polarized $\gamma\gamma$ collider, and could enhance the opacity of $\gamma$-photons in high-energy astrophysical objects to exacerbate the inconsistency between some observations and standard models.

Circularly polarized (CP) $\gamma$-ray sources are versatile for broad applications in nuclear physics, high-energy physics and astrophysics. The laser-plasma based particle accelerators provide accessibility for much higher flux $\gamma$-ray sources than conventional approaches, in which, however, the circular polarization properties of emitted $\gamma$-photons are used to be neglected. In this letter, we show that brilliant CP $\gamma$-ray beams can be generated via the combination of laser plasma wakefield acceleration and plasma mirror techniques. In weakly nonlinear Compton scattering scheme with moderate laser intensities, the helicity of the driving laser can be transferred to the emitted $\gamma$-photons, and their average polarization degree can reach about $\sim 37\%$ ($21\%$) with a peak brilliance of $\gtrsim 10^{21}~$photons/(s $\cdot$ mm$^2 \cdot$ mrad$^2 \cdot$ 0.1% BW) around 1~MeV (100~MeV). Moreover, our proposed method is easily feasible and robust with respect to the laser and plasma parameters.

Generation of arbitrarily spin-polarized lepton (here refer in particular to electron and positron) beams has been investigated in the single-shot interaction of high-energy polarized $\gamma$ photons with an ultraintense asymmetric laser pulse via nonlinear Breit-Wheeler (BW) pair production. We develop a fully spin-resolved semi-classical Monte Carlo method to describe the pair creation and polarization in the local constant field approximation. In nonlinear BW process the polarization of created pairs is simultaneously determined by the polarization of parent $\gamma$ photons, the polarization and asymmetry of scattering laser field, due to the spin angular momentum transfer and the asymmetric spin-dependent pair production probabilities, respectively. In considered all-optical method, dense GeV lepton beams with average polarization degree up to about $80\%$ (adjustable between the transverse and longitudinal components) can be obtained with currently achievable laser facilities, which could be used as injectors of the polarized $e^{+}e^{-}$ collider to search for new physics beyond the Standard Model.