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NiTi powders used for selective laser melting have here been fabricated by the breakup of discontinuous droplets in electrode induction melting gas atomization (EIGA). The morphology, particle size distribution, and hollow ratio of the powder were characterized by scanning electron microscopy (SEM), laser particle size analyzer, and computed tomography (CT), respectively. The effects of gas pressure and catheter length on the particle size distribution and powder morphology were then studied. Furthermore, the effects of the classifier wheel speed on the particle size distribution and yield of the 15–53 μ m powder in the classification process were also analyzed. The results showed that the average particle size (D50) of the NiTi powder first decreased and, thereafter, increased as the atomization gas pressure increased. This was also the situation with catheter length. Also, the yield of the 15–53 μ m powder increased with an increase in the classifier wheel speed. The optimum parameters were a gas atomization pressure of 5 MPa, a tension length of 28 mm, and a classifier wheel speed of 660 r min ^−1 . For this optimized condition, the D50 value and the yield of the NiTi powder were 57.54 μ m and 46.4%. In addition, the flowability, hollow ratio, and oxygen content were 15.8 s/50 g, 0.31%, and 450 ppm, respectively.

We show how two apparently unrelated research areas, namely, strong-field atomic physics and 229Th nuclear physics, are connected. The connection is possible due to the existence of a very low-lying excited state of the 229Th nucleus, which is only about 8 eV above the nuclear ground state. The connection is physically achieved through an electron recollision process, which is the core process of strong-field atomic physics. The laser-driven recolliding electron is able to excite the nucleus, and a simple model is presented to explain this recollision-induced nuclear excitation process. The connection of these two research areas provides novel opportunities for each area and intriguing possibilities from the direct three-partite interplay between atomic physics, nuclear physics, and laser physics. [ABSTRACT FROM AUTHOR]

We present a method to implement the quantum partial search of the database separated into any number of blocks with qudits, D-level quantum systems. Compared with the partial search using qubits, our method needs fewer iteration steps and uses the carriers of the information more economically. To illustrate how to realize the idea with concrete physical systems, we propose a scheme to carry out a twelve-dimensional partial search of the database partitioned into three blocks with superconducting quantum interference devices (SQUIDs) in cavity QED. Through the appropriate modulation of the amplitudes of the microwave pulses, the scheme can overcome the non-identity of the cavity—SQUID coupling strengths due to the parameter variations resulting from the fabrication processes. Numerical simulation under the influence of the cavity and SQUID decays shows that the scheme could be achieved efficiently within current state-of-the-art technology. [ABSTRACT FROM AUTHOR]

We theoretically investigate a fundamental problem in the spring oscillator for a uniformly distributed mass. The wave equation and its solution method are derived in detail. The kinetic energy of the spring and oscillator, the elastic potential energy of the spring, and the oscillating period of the system are solved using a wave equation. Our results show that the total energy and each order harmonic energy of the oscillating system are constant. In addition, the oscillating period of the system is also reported, which is equal to one-third of the spring mass m added to the mass M when m ≤ M. [ABSTRACT FROM AUTHOR]

The dynamical decoupling (DD) method is widely adopted to preserve coherence in different quantum systems. In the case of ideal pulses, its effects on the suppression of noise can be analytically described by the mathematical form of filter function. However, in practical experiments, the unavoidable pulse errors limit the efficiency of DD. In this paper, we study the effects of imperfect pulses on DD efficiency based on quantum trajectories. By directly generating a pseudo noise sequence correlated in time, we can explore the performance of DD with different pulse errors in the typical noise environment. It shows that, for the typical 1/f noise environment, the phase error of operational pulses severely affects the performance of noise suppression, while the detuning and intensity errors have less influence. Also, we get the thresholds of these errors for efficient DD under the given experimental conditions. Our method can be widely applied to guide practical DD experimental implementation. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate the quantum anti-Zeno effect in a two-level system based on a single trapped ion 40Ca+. In the large detuning regime, we show that the transfer from the ground state to the excited state can be remarkably enhanced by the inserted projection measurements. The inserted measurements in our experiment are realized by the electron shelving technique. Compared to the ideal projection measurement, which makes the quantum state collapse instantaneously, a practical electron shelving process needs a finite time duration. The minimum time for this collapse process is shown to be inversely proportional to the square of the coupling strength between the measurement laser and the system. [ABSTRACT FROM AUTHOR]

Calculating the spatial structures of ion crystals is important in ion-trapped quantum computation. Here we demonstrate that the simulated annealing method is a powerful tool to evaluate the structures of ion crystals. By calculating equilibrium positions of 10 ions under harmonic potential and those of 120 ions under anharmonic potential, both with the standard procedure and simulated annealing method, we find that the standard procedure to evaluate spatial structures is complicated and may be inefficient in some cases, and that the simulated annealing method is more favorable. [ABSTRACT FROM AUTHOR]

We present a sub-Doppler cooling scheme of a two-trapped-ion crystal by quantum feedback control method. In the scheme, we obtain the motional information by continuously measuring the spontaneous emission photons from one single ion of the crystal, and then apply a feedback force to cool the whole chain down.We derive the cooling dynamics of the cooling scheme using quantum feedback theory and quantum regression theorem. The result shows that with experimentally achievable parameters, our scheme can achieve lower temperature and faster cooling rate than Doppler cooling. [ABSTRACT FROM AUTHOR]