Catálogo de publicaciones - revistas

<jats:p>Motivated by the fascinating progresses in the cold atom experiments and theories, especially the artificial gauge field induced spin–orbit coupling of neutral atoms, we present a novel dispersion of neutral atoms carrying a non-vanishing magnetic moment in a special gauge field, an external electric field of dark-soliton shaped profile. By means of WKB approximation, we obtain discrete quantized landau-like energy levels, which is instructive for the quantum Hall effect of neutral particles. The observability of the results is also discussed.</jats:p>

<jats:p>Quantum system is inevitably affected by the external environment in the real world. Two controlled quantum dialogue protocols are put forward based on logical <jats:italic>χ</jats:italic>-type states under collective noise environment. One is against collective-dephasing noise, while the other is against collective-rotation noise. Compared with existing protocols, there exist several outstanding advantages in our proposed protocols: Firstly, the <jats:italic>χ</jats:italic>-type state is utilized as quantum channels, it possesses better entanglement properties than GHZ state, <jats:italic>W</jats:italic> state as well as cluster state, which make it difficult to be destroyed by local operations. Secondly, two kinds of logical <jats:italic>χ</jats:italic>-type states are constructed by us in theory, which can be perfectly immune to the effects of collective noise. Thirdly, the controller can be offline after quantum distribution and permission announcement, without waiting for all the participants to complete the information coding. Fourthly, the security analysis illuminates that our protocols can not only be free from the information leakage, but also resist against the intercept-and-resend attack, the entanglement-and-measure attack, the modification attack, the conspiring attack, and especially the dishonest controller’s attacks.</jats:p>

<jats:p>The decoherence of entangled states caused by the noisy channel is a salient problem for reducing the fidelity of quantum communication. Here we present a heralded two-photon entanglement purification protocol (EPP) using heralded high-fidelity parity-check gate (HH-PCG), which can increase the entanglement of nonlocal two-photon polarization mixed state. The HH-PCG is constructed by the input-output process of nitrogen-vacancy (NV) center in diamond embedded in a single-sided optical cavity, where the errors caused by the imperfect interaction between the NV center-cavity system and the photon can be heralded by the photon detector. As the unwanted components can be filtrated due to the heralded function, the fidelity of the EPP scheme can be enhanced considerably, which will increase the fidelity of quantum communication processing.</jats:p>

<jats:p>We investigate the quantum dynamical behaviors of bosons in a diamond chain with weak magnetic flux (WMF), including Landau–Zener tunnelling, Bloch oscillations, localization phenomenon, and collapses-revivals phenomena. We observed that collapses-revivals phenomena can occur in diamond chain with WMF and cannot exist in the strong magnetic flux case as the previous study (Chang N N and Xue J K, 2018, <jats:italic>Chin. Phys. B</jats:italic> <jats:bold>27</jats:bold> 105203). Induced by WMF, the energy band for the system varies from gapless to gapped structure. The position of the extrema of probability amplitude for ground state can also be altered by WMF within a single diamond plaquette. As a consequence, the transitions between different dynamical behaviors of bosons in diamond chain can be manipulated by WMF, depending on its initial configurations.</jats:p>

<jats:p>We analytically and numerically discuss the stability and dynamics of neutral atoms in a two-dimensional optical lattice subjected to an additional harmonic trap potential and artificial magnetic field. The harmonic trap potential plays a key role in modifying the equilibrium state properties of the system and stabilizing the cyclotron orbits of the condensate. Meanwhile, the presence of the harmonic trap potential and lattice potential results in rich cyclotron dynamics of the condensate. The coupling effects of lattice potential, artificial magnetic field, and harmonic trap potential lead to single periodic, multi-periodic or quasi-periodic cyclotron orbits of the condensate. So we can control the cyclotron dynamics of neutral atoms in optical lattice by manipulating the strength of harmonic confinement, artificial magnetic field, and initial conditions. Our results provide a direct theoretical evidence for the cyclotron dynamics of neutral atoms in optical lattices exposed to the artificial gauge magnetic field and harmonic trap potential.</jats:p>

<jats:p>We present two efficient quantum adiabatic algorithms for Bernstein–Vazirani problem and Simon’s problem. We show that the time complexities of the algorithms for Bernstein–Vazirani problem and Simon’s problem are <jats:italic>O</jats:italic>(1) and <jats:italic>O</jats:italic>(<jats:italic>n</jats:italic>), respectively, which are the same complexities as the corresponding algorithms in quantum circuit model. In these two algorithms, the adiabatic Hamiltonians are realized by unitary interpolation instead of standard linear interpolation. Comparing with the adiabatic algorithms using linear interpolation, the energy gaps of our algorithms keep constant. Therefore, the complexities are much easier to analyze using this method.</jats:p>

<jats:p>In most situations, staircase is the only egress to evacuate from high-rise buildings. The merging flow on the stair landing has a great influence on the evacuation efficiency. In this paper, we develop an improved cellular automaton model to describe the merging behavior, and the model is validated by a series of real experiments. It is found that the flow rate of simulation results is similar to the drills, which means that the improved model is reasonable and can be used to describe the merging behavior on stairs. Furthermore, some scenarios with different door locations and building floor numbers are simulated by the model. The results show that (i) the best door location is next to the upward staircase; (ii) the total evacuation time and the building floor number are linearly related to each other; (iii) the pedestrians on upper floors have a negative influence on the evacuation flow rate.</jats:p>

<jats:p>Fluctuation theorems have been applied successfully to any system away from thermal equilibrium, which are helpful for understanding the thermodynamic state evolution. We investigate fluctuation theorems for strong coupling between a system and its reservoir, by path-dependent definition of work and heat satisfying the first law of thermodynamics. We present the fluctuation theorems for two kinds of entropy productions. One is the informational entropy production, which is always non-negative and can be employed in either strong or weak coupling systems. The other is the thermodynamic entropy production, which differs from the informational entropy production at strong coupling by the effects regarding the reservoir. We find that, it is the negative work on the reservoir, rather than the nonequilibrium of the thermal reservoir, which invalidates the thermodynamic entropy production at strong coupling. Our results indicate that the effects from the reservoir are essential to understanding thermodynamic processes at strong coupling.</jats:p>

<jats:p>We propose a low-cost compact microfluidic temperature sensor by virtue of the temperature-dependent permittivity of liquid. The sensor is composed of a coplanar waveguide (CPW) transmission line loaded with three resonators and a microfluidic plate with three channels. The resonant frequency of each resonator relies on the temperature-dependent dielectric property of liquid in corresponding channel, which therefore can be used to extract the temperature. The proposed sensor features a compact size and low cost since it requires only micro fluid volume instead of additional electronic components to produce significant frequency shift with changing temperature. Moreover, it exhibits decent accuracy and stability in a temperature sensing range from 30 °C to 95 °C. A theoretical analysis of the sensor is provided, followed by the detailed characterization method, and a prototype is designed, manufactured, and measured to verify the theoretical analysis.</jats:p>

<jats:p>We present a novel technique for controlling oxygen fugacity, which is broadly used to <jats:italic>in-situ</jats:italic> measure the electrical conductivities in minerals and rocks during diamond anvil cell experiments. The electrical conductivities of olivine are determined under controlled oxygen fugacity conditions (Mo–MoO<jats:sub>2</jats:sub>) at pressures up to 4.0 GPa and temperatures up to 873 K. The advantages of this new technique enable the measuring of the activation enthalpy, activation energy, and activation bulk volume in the Arrhenius relationship. This provides an improved understanding of the mechanism of conduction in olivine. Electrical conduction in olivine is best explained by small polaron movement, given the oxygen fugacity-dependent variations in conductivity.</jats:p>