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<jats:p>Atomic spin relaxation in a vapor cell, which can be characterized by the magnetic resonance linewidth (MRL), is an important parameter that eventually determines the sensitivity of an atomic magnetometer. In this paper, we have extensively studied how the pump intensity affects the spin relaxation. The experiment is performed with a cesium vapor cell, and the influence of the pump intensity on MRL is measured at room temperature at zero-field resonance. A simple model with five atomic levels of a Λ-like configuration is discussed theoretically, which can be used to represent the experimental process approximately, and the experimental results can be explained to some extent. Both the experimental and the theoretical results show a nonlinear broadening of the MRL when the pump intensity is increasing. The work helps to understand the mechanism of pump induced atomic spin relaxation in the atomic magnetometers.</jats:p>

<jats:p>The organic–inorganic hybrid (C<jats:sub>2</jats:sub>H<jats:sub>5</jats:sub>NH<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>CuCl<jats:sub>4</jats:sub> (EA<jats:sub>2</jats:sub>CuCl<jats:sub>4</jats:sub>) single crystals are prepared by the solvothermal condition method. The x-ray diffraction, scanning electron microscopy, dielectric permittivity, pyroelectric current, and heat capacity are used to systematically investigate the electrocaloric performances of EA<jats:sub>2</jats:sub>CuCl<jats:sub>4</jats:sub>. The pyroelectric currents are measured under various voltages, and the electrocaloric effect (ECE) is calculated. Its ECE exhibits an isothermal entropy change of 0.0028 J/kg · K under an electric field of 30 kV/cm associated with a relatively broad temperature span. Further, the maximum pyroelectric coefficient (<jats:italic>p</jats:italic>) is 4× 10<jats:sup>−3</jats:sup> C/m<jats:sup>21</jats:sup> · K and the coefficient <jats:italic>β</jats:italic> for generating ECE from electric displacement <jats:italic>D</jats:italic> is 1.068× 10<jats:sup>8</jats:sup> J · cm · K<jats:sup>−1</jats:sup> · C<jats:sup>−2</jats:sup> at 240 K. Our results indicate that the ECE behavior of organic–inorganic hybrid EA<jats:sub>2</jats:sub>CuCl<jats:sub>4</jats:sub> is in accordance with Jona and Shirane’s opinion in which the ECE should occur both below and above the Curie temperature <jats:italic>T</jats:italic> <jats:sub>c</jats:sub>.</jats:p>

<jats:p>The InAs/AlSb heterostructures with step-graded GaAs<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sb<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub> metamorphic buffer layers grown on Si substrates by molecular beam epitaxy are studied. The step-graded GaAs<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sb<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub> metamorphic buffer layers are used to relax the strain and block defects at each interface of the layers. Meanwhile, adding Sb to GaAs is also beneficial to suppressing the formation of dislocations in the subsequent materials. The influences of the growth temperature of the step-graded GaAs<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sb<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub> metamorphic buffer layer on the electron mobility and surface topography are investigated for a series of samples. Based on the atomic force microscopy (AFM), high resolution x-ray diffraction (HRXRD), reciprocal space map (RSM), and Hall measurements, the crystal quality and composition of GaAs<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sb<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub> layer are seen to strongly depend on growth temperature while keeping the Ga growth rate and V/III ratio constant. The results show that the highest electron mobility is 10270 cm<jats:sup>2</jats:sup>/V·s and the roughness is 4.3 nm for the step-graded GaAs<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sb<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub> metamorphic buffer layer grown at a temperature of 410 °C.</jats:p>

<jats:p>Indium phosphide (InP) quantum dots (QDs) have shown great potential to replace the widely applied toxic cadmium-containing and lead perovskite QDs due to their similar emission wavelength range and emission peak width but without intrinsic toxicity. Recently, electrically driven red and green InP-based quantum-dot light-emitting diodes (QLEDs) have achieved great progress in external quantum efficiency (EQE), reaching up to 12.2% and 6.3%, respectively. Despite the relatively poor device performance comparing with cadmium selenide (CdSe)- and perovskite-based QLEDs, these encouraging facts with unique environmental friendliness and solution-processability foreshadow the enormous potential of InP-based QLEDs for energy-efficient, high-color-quality thin-film display and solid-state lighting applications. In this article, recent advances in the research of the InP-based QLEDs have been discussed, with the main focus on device structure selection and interface research, as well as our outlook for on-going strategies of high-efficiency InP-based QLEDs.</jats:p>

<jats:p>The applications of magnetrons are greatly limited because of the poor output spectrum of the free-running magnetron. Currently, one of the best ways to solve this problem is injection locking. However, the injection locking theory which is widely used nowadays is based on the simplified oscillator, which does not include the frequency pushing effect of the magnetron. In this paper, the theory of injection locking magnetrons with frequency pushing effect is systematically studied. Analytical analysis shows that the locking bandwidth turns larger with the consideration of the pushing parameter (<jats:italic>α</jats:italic>), and the increase of locking bandwidth is expanded with <jats:italic>α</jats:italic> increasing. Experimental results show that the locking bandwidth is expanded by 0.3 MHz, 1 MHz, and 1.6 MHz compared with the locking bandwidth from the conventional locking theory under an injection ratio (<jats:italic>ρ</jats:italic>) of 0.05, 0.075, and 0.1, respectively. This research provides a more accurate prediction of the properties of the injection-locked magnetron.</jats:p>

<jats:p>Antenna-coupled field-effect-transistors (FETs) offer high sensitivity for terahertz detection. Both the magnitude and the polarity of the response signal are sensitive to the localized terahertz field under the gate. The ability of accurate sensing the intensity pattern is required for terahertz imaging systems. Here, we report artefacts in the intensity pattern of a focused terahertz beam around 1 THz by scanning a silicon-lens and antenna coupled AlGaN/GaN high-electron-mobility-transistor (HEMT) detector. The origin of the image distortion is found to be connected with one of the antenna blocks by probing the localized photocurrents as a function of the beam location and the frequency. Although the exact distortion is found with our specific antenna design, we believe similar artefacts could be commonplace in antenna-coupled FET terahertz detectors when the beam spot becomes comparable with the antenna size. To eliminate such artefacts, new antenna designs are welcomed to achieve strong asymmetry in the terahertz field distribution under the gate while maintaining a more symmetric radiation pattern for the whole antenna.</jats:p>

<jats:p>We exhibit some new dark soliton phenomena on the general nonzero background for a defocusing three-component nonlinear Schrödinger equation. As the plane wave background undergoes unitary transformation <jats:italic>SU</jats:italic>(3), we obtain the general nonzero background and study its modulational instability by the linear stability analysis. On the basis of this background, we study the dynamics of one-dark soliton and two-dark-soliton phenomena, which are different from the dark solitons studied before. Furthermore, we use the numerical method for checking the stability of the one-dark-soliton solution. These results further enrich the content in nonlinear Schrödinger systems, and require more in-depth studies in the future.</jats:p>

<jats:p>For the unsorted database quantum search with the unknown fraction <jats:italic>λ</jats:italic> of target items, there are mainly two kinds of methods, <jats:italic>i.e.</jats:italic>, fixed-point and trail-and-error. (i) In terms of the fixed-point method, Yoder <jats:italic>et al</jats:italic>. [<jats:italic>Phys. Rev. Lett</jats:italic>. <jats:bold>113</jats:bold> 210501 (2014)] claimed that the quadratic speedup over classical algorithms has been achieved. However, in this paper, we point out that this is not the case, because the query complexity of Yoder’s algorithm is actually in <jats:inline-formula> <jats:tex-math><?CDATA $O(1/\sqrt{{\lambda }_{0}})$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> <mml:msqrt> <mml:mrow> <mml:msub> <mml:mi>λ</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:msqrt> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_12_120301_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> rather than <jats:inline-formula> <jats:tex-math><?CDATA $O(1/\sqrt{\lambda })$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> <mml:msqrt> <mml:mi>λ</mml:mi> </mml:msqrt> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_12_120301_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, where <jats:italic>λ</jats:italic> <jats:sub>0</jats:sub> is a known lower bound of <jats:italic>λ</jats:italic>. (ii) In terms of the trail-and-error method, currently the algorithm without randomness has to take more than 1 times queries or iterations than the algorithm with randomly selected parameters. For the above problems, we provide the first hybrid quantum search algorithm based on the fixed-point and trail-and-error methods, where the matched multiphase Grover operations are trialed multiple times and the number of iterations increases exponentially along with the number of trials. The upper bound of expected queries as well as the optimal parameters are derived. Compared with Yoder’s algorithm, the query complexity of our algorithm indeed achieves the optimal scaling in <jats:italic>λ</jats:italic> for quantum search, which reconfirms the practicality of the fixed-point method. In addition, our algorithm also does not contain randomness, and compared with the existing deterministic algorithm, the query complexity can be reduced by about 1/3. Our work provides a new idea for the research on fixed-point and trial-and-error quantum search.</jats:p>

<jats:p>This paper studies quantum discord of two qutrits coupled to their own environments independently and coupled to the same environment simultaneously under quantum-jump-based feedback control. Our results show that spontaneous emission, quantum feedback parameters, classical driving, initial state, and detection efficiency all affect the evolution of quantum discord in a two-qutrit system. We find that under the condition of designing proper quantum-jump-based feedback parameters, quantum discord can be protected and prepared. In the case where two qutrits are independently coupled to their own environments, classical driving, spontaneous emission, and low detection efficiency have negative effect on the protection of quantum discord. For different initial states, it is found that the evolution of quantum discord under the control of appropriate parameters is similar. In the case where two qutrits are simultaneously coupled to the same environment, the classical driving plays a positive role in the generation of quantum discord, but spontaneous emission and low detection efficiency have negative impact on the generation of quantum discord. Most importantly, we find that the steady discord depends on feedback parameters, classical driving, and detection efficiency, but not on the initial state.</jats:p>

<jats:p>Gilad Gour and Nolan R Wallach [<jats:italic>J. Math. Phys.</jats:italic> <jats:bold>51</jats:bold> 112201 (2010)] have proposed the 4-tangle and the square of the I concurrence. They also gave the relationship between the 4-tangle and the square of the I concurrence. In this paper, we give the expression of the square of the I concurrence and the <jats:italic>n</jats:italic>-tangle for six-qubit and eight-qubit by some local unitary transformation invariant. We prove that in six-qubit and eight-qubit states there exist strict monogamy laws for quantum correlations. We elucidate the relations between the square of the I concurrence and the <jats:italic>n</jats:italic>-tangle for six-qubit and eight-qubits. Especially, using this conclusion, we can show that 4-uniform states do not exist for eight-qubit states.</jats:p>