Physics of Particles and Nuclei最新文献

In this research we present a modified version of the simplified quantum hash function that provides improved encoding capabilities and allows to double the amount of classical information stored in the series of single-qubit states. We give the analysis of the one-way property and collision resistance of the proposed function.

We review the relic density of dark matter in the non-standard cosmological scenarios which includes kination models, brane world cosmology and shear dominated universe. Then we use the Planck data to find constraints on the parameter spaces as dark matter cross sections and the five dimentional Planck mass for brane cosmology, enhancement factor for kination model and the inverse-scaled shear temperature for shear dominated universe.

Simulation of the Quantum Approximate Optimization Algorithm (QAOA) was performed using the Cirq software library installed on the HybriLIT quantum computing testbed at JINR. The problem of finding the lowest energy state for the Ising model with a longitudinal magnetic field was solved for two- and three-dimensional lattices of various sizes. Quantum circuits with registers up to 27 qubits were investigated during the study. Optimization of the variational ansatz parameters was carried out using both gradient-based and gradient-free methods. The processes and results of optimization carried out by various methods were compared by a number of parameters.The influence of the configuration of the computing resources used on the efficiency of calculations has been demonstrated.

Transport of ballistic electrons through a 1D-dimensional quantum ring (subjected to Rashba spin–orbit interaction), connected with two external leads, is studied in the presence of external fields. These fields include the optical radiation, produced by an off-resonant high-frequency electric field, and a perpendicular magnetic field. With the aid of the Floquet theory, the key role of the interplay between the optical radiation intensity and the Rashba interaction is established for spin filtering effect of an initially arbitrary polarized electron beam at zero and low magnetic fields.

A formulation of quantum mechanics based on replacing the general unitary group by finite groups is considered. To solve problems arising in the context of this formulation, we use computer algebra and computational group theory methods.

Search for reactions with nucleon charge exchange in the fragmentation of carbon nuclei with the energy of 300 MeV/nucleon on a thin beryllium target is performed on the FRAGM fragment separator of the TWAC accelerator complex. The experimental setup arranged at the angle of 3.5° with respect to the incident beam has a high momentum resolution. Differential cross sections for yields of ¹¹Be, ¹²B, and ¹²Be nuclei are measured as a function of the momentum of these nuclei. The experimental data are compared with theoretical predictions of various nucleus–nucleus interaction models and other experimental results. Nucleon charge-exchange processes in this energy range are measured for the first time. New data are obtained for verification of theoretical models of nucleus–nucleus interactions.

This article presents a technology being developed for the design of an intelligent robust control system based on quantum and soft computing. The corresponding software tools and stages of creating an embedded control system are presented. In particular, the application of soft computing, fuzzy logic, fuzzy neural networks, and evolutionary and quantum computing using quantum-inspired algorithms implemented on classical processors is considered. As an illustrative example, the problem of controlling refrigerant pressure during testing of superconducting magnets is addressed. The results of applying a coordination control system with an integrated quantum controller are presented.

The issue of the dichotomy between the elementary and composite nature of a finite-dimensional quantum system is discussed within the framework of the generalized Stratonovich–Weyl formulation of quantum mechanics. Performing numerical studies, we demonstrate how information on the possibility of realizing a virtual 2-level subsystem is encoded in the properties of the Wigner function of a total 4-level system.

We consider an (n)-qubit quantum system with a Hamiltonian, defined by an expansion in the Pauli basis, and propose a new algorithm for classical computing the exponential of the Hamiltonian. The algorithm is based on the representation of the exponential by the Dunford–Cauchy integral, followed by an efficient computation of the resolvent, and is suitable for Hamiltonians that are sparse in the Pauli basis. The practical efficiency of the algorithm is demonstrated by two illustrative examples.

The model of multi-level open quantum system interacting with a non-vacuum reservoir in the rotating wave approximation is considered. We provide an exact integral representation for the reduced density matrix of the system. For identical uncorrelated reservoirs in diagonal states we have obtained the first perturbative correction for such dynamics in the Bogolubov–van Hove limit. We have shown that after initial state renormalization it can be completely described in terms of finite-dimensional semigroup. The method we provide can also be applied to the further orders of perturbation theory with Bogolubov–van Hove scaling.