SPIN

People are witnessing quantum computing revolutions nowadays. Progress in the number of qubits, coherence times and gate fidelities is happening. Although quantum error correction era has not arrived, the research and development of quantum computing have inspired insights and breakthroughs in quantum technologies, both in theories and in experiments. In this review, we introduce the basic principles of quantum computing and the multilayer architecture for a quantum computer. There are different experimental platforms for implementing quantum computing. In this review, based on a mature experimental platform, the Nuclear Magnetic Resonance (NMR) platform, we introduce the basic steps to experimentally implement quantum computing, as well as the common challenges and techniques.

In this communication, the synthesis (solid-state sintering) and characterization of a double perovskite BiFeMoO₆ are reported. Analysis of X-ray diffraction (XRD) data provides monoclinic crystal symmetry with an average crystallite size of 85.6nm and lattice strain of 0.00078, respectively. The microstructural analysis of the sample was done using a scanning electron microscope (SEM) and the results show that grains are well-grown and distributed uniformly throughout the sample surface. The grains are visible clearly due to well-defined grain boundaries, and the effect on the mechanism of electrical ac conductivity was studied. The compositional purity of the sample was checked by energy dispersive X-ray (EDX) analysis spectrum which supports the presence of all constituent elements (Bi, Fe, Mo and O) in both weight and atomic percentages. The study of the Ultraviolet–Visible spectrum provides a bandgap energy of 1.8eV, suitable for photovoltaic applications. The measurements of the dielectric were used to confirm the existence of the Maxwell–Wagner type of dispersion. The study of impedance spectroscopy helps to understand the negative temperature coefficient of resistance (NTCR) character while the electrical modulus measurements claimed a non-Debye relaxation mechanism in the sample. The study of ac conductivity reveals the fact of thermally activated conduction mechanism in the sample. The presence of the semiconducting nature of the sample was checked from both Nyquist plots and Cole–Cole plots. The study of the resistance versus temperature reveals the fact of negative temperature coefficient (NTC) thermistor character and is suitable for some temperature sensor devices.

In this paper, the structural, electronic, magnetic, and half-metallic properties of full-Heusler alloys Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) in the Hg₂CuTi-type structure have been studied by using the first-principles-based density functional theory (DFT) with the full-potential linearized augmented plane-wave (FP-LAPW) method. Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) compounds are found to be half-metallic ferrimagnets. The calculated total magnetic moments of the Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) alloys are estimated at 01${\mu }_B$ according to the Slater–Pauling rule of $M_{\mathrm{\text{tot}}}=$ ($Z_{\mathrm{\text{tot}}}$–24) ${\mu }_B$. It was discovered that Mn₂ZrAs and Mn₂ZrBi maintained their half-metallicity for a lattice constant interval of 5.72 to 6.26 Å and 6.33 to 6.62 Å, respectively, and present a maximum degree of spin polarization at the Fermi level. In addition, the predicted formation energy and elastic parameters show that these materials are mechanically stable. All of these results indicate that these new Mn₂-based heusler alloys are able to be the candidates for spintronic applications.

Due to the large state space of the two-qubit system, and the adoption of ladder reward function in the existing quantum state preparation methods, the convergence speed is slow and it is difficult to prepare the desired target quantum state with high fidelity under limited conditions. To solve the above problems, a difference-driven reinforcement learning (RL) algorithm for quantum state preparation of two-qubit system is proposed by improving the reward function and action selection strategy. Firstly, a model is constructed for the problem of preparing quantum states of a two-qubit system, with restrictions on the type of quantum gates and the time for quantum state evolution. In the preparation process, a weighted differential dynamic reward function is designed to assist the algorithm quickly obtain the maximum expected cumulative reward. Then, an adaptive $\epsilon$-greedy action selection strategy is adopted to achieve a balance between exploration and utilization to a certain extent, thereby improving the fidelity of the final quantum state. The simulation results show that the proposed algorithm can prepare quantum state with high fidelity under limited conditions. Compared with other algorithms, it has different degrees of improvement in convergence speed and fidelity of the final quantum state.

By using the density functional theory, we have studied the electronic structure and magnetism of the oxygen vacancy defect in GdCoO₃ perovskite compound. We have carried out a magnetic stability calculation; between many possible magnetic configurations, the ferromagnetic ordering was predicted in both gadolinium and cobalt sublattices. We have demonstrated that the oxygen vacancy defect causes a ferromagnetic order via a mixture of octahedral HS Co${}^{3+}$, tetrahedral HS Co${}^{2+}$ and octahedral IS Co${}^{3+}$. From the spin magnetic moment and partial density of state investigation, we have predicted an induced long-range ferromagnetic ordering in nonstoichiometric GdCoO${}_{3-\delta }$.

The exciting properties of multi-valued logic (MVL) in overcoming the limitations of binary systems have led to widespread research on this topic. Considering various types of MVL, quaternary logic is more compatible with the existing binary systems. This paper proposes a nonvolatile quaternary flip-flop (NQFF) based on the unique features of the carbon nanotube field-effect transistors (CNTFETs) and magnetic tunnel junctions (MTJs). The proposed NQFF utilizes Spin-Hall effect (SHE)-assisted spin-transfer torque (STT) MTJs to provide nonvolatility with lower write energy, and multi-Vt gate-all-around (GAA) CNTFETs offer higher performance. On the other side, due to the usage of a shadow latch and the design of the proposed circuit, the delay of MTJ switching does not affect the delay of the whole circuit. The simulation results show that the proposed NQFF offers 50% lower PDP when the system is idle for only 25% of its total operational time.

The electron tunneling in ZnO/ZnCdO semiconductor heterostructure is studied using the matrix method. The spin-polarization is examined due to Dresselhaus spin–orbit interaction and Rashba spin–orbit interaction. The total spin-polarization is mainly due to Dresselhaus spin–orbit interaction and the Rashba spin–orbit interaction is small. The high degree of spin polarization can be achieved at a high barrier width. With the increasing cadmium concentration in this heterostructure, the spin polarization efficiency is enhanced. The dwell time is reported and discussed.

The dielectric properties of a monolayer phenanthrene-like nanoisland of formula B${}_{14}$A${}_{10}$ are examined in this research using Monte Carlo simulations. We evaluate the behaviors of the electric hysteresis loops and blocking temperature under the exchange coupling, crystalline field and temperature effects. The multi-loop hysteresis behavior examined in this research may have beneficial applications in nanotechnology and multi-state memory storage. Besides, the results found in the Phenanthrene-like nanoisland are in good agreement with several theoretical and experimental results.

Currently, static circuit power is becoming a major concern, dominating the total power consumption due to the scaling down of CMOS technology. The smaller sizes drastically affect the leakage current, which integrated circuit designers attempt to overcome this issue. Hence, several methods and technologies have been proposed to prevail this phenomenon. One of these methods is using memory structures in logic designs. A Hybrid MTJ/CMOS circuit is one of these promising techniques to design low-power nonvolatile circuits with power gating ability and low overhead for reconfigurable possibilities. In this paper, we have proposed a fully nonvolatile, low-power Full-Adder based on MTJs that uses the spin transfer torque method assisted by the spin hall effect. Simulation results of these designs by HSPICE show that they can work fast with low-power consumption compared to other state-of-the-art nonvolatile full-adders.

Shrinking the transistor dimensions in complementary metal-oxide-semiconductor (CMOS) technology has led to many huge problems, like high power density. Various methods at different design levels of abstraction, such as approximate computing and spintronic devices based on magnetic tunnel junction (MTJ), have been studied to solve these problems. In this paper, we propose a novel hybrid MTJ/FinFET-based approximate 5:2 compressor. The proposed design employs the spin-transfer torque (STT) method assisted by the spin-Hall effect (SHE) to store inputs in MTJs. Due to the SHE assistance, the energy efficiency of the MTJ switching is improved considerably over the conventional STT method. Our design significantly improves the energy consumption compared to the previous compressors, thanks to the decrease in MTJ and transistor counts. The proposed circuit and previous designs are simulated using HSPICE with 7-nm FinFET and SHE perpendicular-anisotropy MTJ model. From the simulation results, we can see that the proposed design improves power consumption, write energy, read energy, number of transistors and MTJ count on average by 49%, 50%, 63%, 20% and 50%, respectively, in comparison with the existing counterparts. Furthermore, the accuracy of the approximate designs is evaluated through comprehensive MATLAB simulations. The results indicate that the proposed circuit outperforms the best previous energy-efficient designs in terms of accuracy despite having better hardware characteristic parameters.