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<jats:p> <jats:italic>We demonstrate a long-coherent-time coupling between microwave and optical fields through cold atomic ensembles. The phase information of the microwave field is stored in a coherent superposition state of a cold atomic ensemble and is then read out by two optical fields after 12 ms. A similar operation of mapping the phase of optical fields into a cold atomic ensemble and then retrieving by microwave is also demonstrated. These studies demonstrate that long-coherent-time cold atomic ensembles could resonantly couple with microwave and optical fields simultaneously, which paves the way for realizing high-efficiency, high-bandwidth, and noiseless atomic quantum converters</jats:italic>.</jats:p>

<jats:p> <jats:italic>An elongated trap potential for cold atoms is designed based on a quadrupole-Ioffe configuration. Phase fluctuations in a Bose–Einstein condensate (BEC), which is confined by the trap, are studied. We simulate the atom density distribution induced by fluctuation after time of flight from this elongated trap potential and study the temperature measurement method related to the distribution. Furthermore, taking advantage of the tight confinement and radio frequency dressing technique, we propose a double well potential for splitting BECs. Our results are helpful for improving understanding of low-dimensional quantum gases and provide important guidance for atomic interferometry</jats:italic>.</jats:p>

<jats:p> <jats:italic>The definitions of strong superadditive deficit for relative entropy coherence and monogamy deficit of measurement-dependent global quantum discord are proposed. The equivalence between them is proved, which provides a useful criterion for the validity of the strong superadditive inequality of relative entropy coherence. In addition, the strong superadditive deficit of relative entropy coherence is proved to be greater than or equal to zero under the condition that bipartite measurement-dependent global quantum discord (GQD) does not increase under the discarding of subsystems. Using the Monte Carlo method, it is shown that both the strong superadditive inequality of relative entropy coherence and the monogamy inequality of measurement-dependent GQD are established under general circumstances. The bipartite measurement-dependent GQD does not increase under the discarding of subsystems. The multipartite situation is also discussed in detail</jats:italic>.</jats:p>

<jats:p> <jats:italic>Quantum contextuality is one kind of quantumness that distinguishes quantum mechanics from classical theory. As the simplest exclusivity graph, quantum contextuality of the n-cycle graph has been reviewed, while only for odd n the quantumness can be revealed. Motivated by this, we propose the degree of non-commutativity and the degree of uncertainty to measure the quantumness in the n-cycle graphs. As desired, these two measures can detect the quantumness of any n-cycle graph when n ≥ 4</jats:italic>.</jats:p>

<jats:p> <jats:italic>In the traditional random-conformational-search model, various hypotheses with a series of meta-stable intermediate states were proposed to resolve the Levinthal paradox in protein-folding time. Here we introduce a quantum strategy to formulate protein folding as a quantum walk on a definite graph, which provides us a general framework without making hypotheses. Evaluating it by the mean of first passage time, we find that the folding time via our quantum approach is much shorter than the one obtained via classical random walks. This idea is expected to evoke more insights for future studies</jats:italic>.</jats:p>

<jats:p> <jats:italic>An absorption-desorption model with long-ranged interaction is simulated by the dynamic Monte Carlo method. The dynamic process has an inert phase and an active phase that is controlled by the absorption rate. In the active phase, the number of vacancies increases with time exponentially, while in the inert phase the vacant sites will be occupied by adsorbates rapidly. At the critical absorption rate, both the number of vacancies and the time-depending active probability exhibit power-law behavior. We determine the critical absorption rate and the scaling exponents of the power-laws. The effect of the interaction range of desorption on the critical exponents is investigated. In the short-ranged interaction limit, the critical exponents of Schlögl’s first model are recovered. The model may describe the stability of the inner Helmholtz layer, an essential component of the electrochemical double-layer capacitor at a nanowire.</jats:italic> </jats:p>

<jats:p> <jats:italic>Using the Debye shielding model, the effects of plasma shielding on the dielectronic recombination processes of the H-like helium ions are investigated. It is found that plasma shielding causes a remarkable change in the Auger decay rate of the doubly excited 2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup> <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>2</jats:sub> state. As a result, the dielectronic recombination cross sections from the doubly excited 2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup> <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>2</jats:sub> state increases with the decreasing Debye shielding length.</jats:italic> </jats:p>

<jats:p> <jats:italic>High-brightness tapered lasers with photonic crystal structures are designed and fabricated. A narrow taper angle is designed for the tapered section. The device delivers an output power of 3.3 W and a maximum wall-plug efficiency of 43%. The vertical beam divergence is around 11° at different currents. Nearly diffraction-limited beam qualities for the vertical and lateral directions are obtained. The lateral beam quality factor <jats:italic>M</jats:italic> <jats:sup>2</jats:sup> is below 2.5 and the vertical <jats:italic>M</jats:italic> <jats:sup>2</jats:sup> value is around 1.5 across the whole operating current range. The maximum brightness is 85 MW·cm<jats:sup>−2</jats:sup>sr<jats:sup>−1</jats:sup>. When the current is above 3.3 A, the brightness is still above 80 MW·cm<jats:sup>−2</jats:sup>sr<jats:sup>−1</jats:sup>.</jats:italic> </jats:p>

<jats:p> <jats:italic>A silicon shallow-ridge waveguide integrated superconducting nanowire single photon detector is designed and fabricated. At the bias current of 11.6 μA, 4% on-chip detection efficiency near 1550 nm wavelength is achieved with the dark count rate of 3 Hz and a timing jitter of 75 ps. This device shows the potential application in the integration of superconducting nanowire single photon detectors with a complex quantum photonic circuit.</jats:italic> </jats:p>

<jats:p> <jats:italic>Considered to be a candidate for large-size bulk materials used in lasers and other fields, Nd<jats:sup>3+</jats:sup>-doped glass ceramics containing NaYF<jats:sub>4</jats:sub> nanocrystallites are prepared. Using x-ray diffraction and transmission electron microscopy, we show that pure cubic NaYF<jats:sub>4</jats:sub> is well precipitated in the glass matrix. To obtain the optical property of this material at 1.06 μm, the fluorescence decay of <jats:sup>4</jats:sup> <jats:italic>F</jats:italic> <jats:sub>3/2</jats:sub> energy levels is measured and analyzed. It is found that the fluorescence lifetime decreases first and then increases with the increasing dopant concentration due to the existing but finally weakening energy dissipation. As a result, a long radiation lifetime of about 191–444 μs is obtained at 1.06 μm in the prepared material. It is thus revealed that Nd<jats:sup>3+</jats:sup>-doped glass ceramic containing NaYF<jats:sub>4</jats:sub> nanocrystallites is a potential candidate as a near-infrared laser material.</jats:italic> </jats:p>