International Journal of Modern Physics B

This article reviews recent progress in quantum database search algorithms. The subject is presented in a self-contained and pedagogical way. The problem of searching a large database (a Hilbert space) for a target item is performed by the famous Grover algorithm which locates the target item with high probability and a quadratic speed-up compared with the corresponding classical algorithm. If the database is partitioned into blocks and one is searching for the block containing the target item instead of the target item itself, then the problem is referred to as partial search. Partial search trades accuracy for speed and the most efficient version is the Grover–Radhakrishnan–Korepin (GRK) algorithm. The target block can be further partitioned into sub-blocks so that GRK's can be performed in a sequence called a hierarchy. We study the Grover search and GRK partial search in detail and prove that a GRK hierarchy is less efficient than a direct GRK partial search. Both the Grover search and the GRK partial search can be generalized to the case with several target items (or target blocks for a GRK). The GRK partial search algorithm can also be represented in terms of group theory.

Magnetometers based on Superconducting Quantum Interference Device (SQUID) are widely employed in high sensitivity magnetometry. In particular, new multichannel systems for biomagnetic applications require many sensors which are very close to each other giving the crosstalk disturbance between the neighboring channel. Here, we present experimental results about a fully integrated dc-SQUID magnetometer, based on niobium technology, having a suitable design which allows to reduce crosstalk due to both the feedback coil and wires.

The crosstalk level measurements relative to a particular arrangement of sensors are reported. In such configuration, four magnetometers are placed over a square board 30 mm in side with a distance between their sensor centers of 14 mm. The measurements have been performed in a ⁴He cryostat at T = 4.2 K in a flux-locked loop configuration using a readout electronics with a direct coupled scheme. The experimental data have shown a substantial reduction of crosstalk among neighboring sensors with respect to a traditional feedback coil. Furthermore, the field noise measurements have ensured that the new pickup and feedback coils design does not introduce any noise level degradation.

This paper studies the problem of chaotic synchronization of the fractional-order modified coupled dynamos system, designs the activate controllers, and then proves that the self-synchronization of the fractional-order modified coupled dynamos system and the fractional-order modified coupled dynamos system's different structure synchronization with the fractional-order Lorenz system can both arrive theoretically. The simulation results demonstrate the validity of the activate controller.

The transport properties of sintered samples of NdBa_2-x La_xCu₃O_7-δ with 0 ≤ x ≤ 0.3 have been studied in the normal state by Hall effect measurements. The Hall coefficient, R_H is positive in the normal state and increases with increasing La doping concentration over the whole temperature range from the critical temperature, T_c, up to room temperature. The results for the Hall coefficient as a function of temperature and doping concentration were analyzed within the phenomenological narrow band and Anderson models. A good agreement between models and data was obtained. As in the phenomenological narrow band model, the band widths increase with increasing doping concentration. As in the Anderson model, the Hall angle is proportional to T² over the whole measured temperature range for all samples. The obtained results for both models supported the view that La doping introduces electronic disorder into the CuO₂ planes. The tendency towards localization is driven by electronic disorder. In addition to hole filling, the localization is another reason for the decreasing superconducting critical temperature in these samples.

One-dimensional Heisenberg antiferromagnets can be described by the O(3) nonlinear σ-model (NLσM). We give a review on zero temperature and finite temperature Haldane gaps obtained from this model. Based on the coupled-chain theory, we derive the finite temperature Haldane gap for triangular antiferromagnet RbNiCl₃. The Néel temperature is obtained as 11 K. In order to treat the anisotropy in crystal Ni(C₂H₈ N₂)₂NO₂(ClO₄), we relax the constraint of the NLσM and compute the finite temperature Haldane gap using a Ginzburg–Landau mean field approach. The comparison with the experimental data is discussed.

Analytic approximations for the absorption coefficient and refraction index have been obtained for a two-level molecular system in the presence of a four-wave mixing signal. Stochastic collisions among solute–solvent molecules produce a broadening of the upper level of energy. In this work, we have used four generalized Lorentzian approximants of the Voigt function as probability distribution, calculated by the two-point quasi-rational approximant method previously denoted as asymptotical Padé technique, for the evaluation of the average values of the Fourier components associated to the induced coherences. The innovation of this type of distributions allows us, by taking appropriate limits, to find similar profiles of optical properties as those using Gaussian and Lorentzian distribution functions.

Calcium phosphate (CaP) compounds like hydroxyapatite and tricalcium phosphates are considered to be very important biomaterials. This study used RF-magnetron sputtering (RF-MS) to deposit CaP onto 316L SS. Due to the complex nature of the effect of different sputtering parameters on the quality and integrity of the coatings, there is a need to further investigate those parameters collectively. An L₉(3⁴) orthogonal array was employed to design the experiment that was used to investigate four important coating parameters which include RF-power, argon gas flow rate, deposition time and post-heat treatment conditions. The coating composition and structure were evaluated using XRD, EDX and FTIR. The mechanical property was measured in terms of the adhesion strength using a microscratch testing machine. The response graph of the results revealed that the interfacial strength of CaP was mainly influenced by the deposition power, while the coating thickness was predominantly affected by the argon gas flow rate. High adhesion strength was achieved when the coatings have at least 2 μm thickness and deposited at a working pressure of 12 m Torr. ANOVA on the control factors helped rank the parameters accordingly in order of importance. Based on the response of the control factors, it was found that optimum adhesion strength could be achieved by depositing the coatings using the following parameters: 10 sccm of argon gas flow rate; 150 W of RF power; and 16 h of deposition.

Although the stable structures and other physical properties of small Ag_n and Au_n, were investigated in the literature, phonon calculations are not done yet. In this work, we present plane-wave pseudopotential calculations based on density-functional formalism. The effect of using the generalized gradient approximation (GGA) and local density approximation (LDA) to determine the geometric and electronic structure and normal mode calculations of Ag_n and Au_n, is studied up to eight atoms. Pure Au_n and Ag_n clusters favor planar configurations. We calculated binding energy per atom. We have also calculated the normal mode calculations and also scanning tunneling microscope (STM) images for small clusters for the first time.

The Davydov's soliton propagation in the linear polymer chain is analyzed numerically by solving the discrete equations of motion for exciton and phonon amplitudes. The main difference with respect to the results of continual approximation is that two exciton–phonon coupling constants influence separately the soliton behavior. Their influence is studied both in the ideal chain and the chain with single impurity.

Large-scale replication of the natural process of photosynthesis is a crucial subject of storing solar energy and saving our environment. Here, we report femtosecond laser induced self-assembled metal nanostructure arrays, which are easily mass producible on earth-abundant metals, can directly synthesize liquid and solid hydrocarbon compounds from carbon dioxide, water, and sunlight at a production rate of more than 1 × 10⁵ μL/(gh) that is significantly (10³–10⁶ times) higher than those in previous studies.^1,2 The efficiency for storing solar energy of the photosynthesis is about 10% in the present simple experimental setup which can be further improved. Moreover, different from previous artificial photosynthesis works, this phenomenon presents a new mechanism that, through a surface-enhanced photodissociation process, nature-like photosynthesis can be performed artificially.