The study of amplitude and phase relaxation impact on the quality of quantum information technologies

The influence of amplitude and phase relaxation on evolution of quantum states within the formalism of quantum operations is considered. The model of polarizing qubits where noises are determined by the existence of spectral degree of freedom that shows up during the light propagation inside anisotropic mediums with dispersion is studied. Approximate analytic model for calculation of phase plate impact on polarizing state with dispersion influence taken into consideration is suggested.Comment: 7 pages, 4 figures, report for the International Symposium "Quantum Informatics-2014" (QI-2014), Zvenigorod, Moscow region, October 06-10, 201

Numerical and analytical research of the impact of decoherence on quantum circuits

Three different levels of noisy quantum schemes modeling are considered: vectors, density matrices and Choi-Jamiolkowski related states. The implementations for personal computers and supercomputers are described, and the corresponding results are shown. For the level of density matrices, we present the technique of the fixed rank approximation and show some analytical estimates of the fidelity level.Comment: 11 pages, 9 figures, report for the International Symposium "Quantum Informatics-2014" (QI-2014), Zvenigorod, Moscow region, October 06-10, 201

Fast reconstruction of programmable integrated interferometers

Programmable linear optical interferometers are important for classical and quantum information technologies, as well as for building hardware-accelerated artificial neural networks. Recent results showed the possibility of constructing optical interferometers that could implement arbitrary transformations of input fields even in the case of high manufacturing errors. The building of detailed models of such devices drastically increases the efficiency of their practical use. The integral design of interferometers complicates its reconstruction since the internal elements are hard to address. This problem can be approached by using optimization algorithms [Opt. Express 29, 38429 (2021)]. In this paper, we present a novel efficient algorithm based on linear algebra only, which does not use computationally expensive optimization procedures. We show that this approach makes it possible to perform fast and accurate characterization of high-dimensional programmable integrated interferometers. Moreover, the method provides access to the physical characteristics of individual interferometer layers

Fast reconstruction of programmable interferometers with intensity-only measurements

Programmable linear optical interferometers are promising for classical and quantum applications. Their integrated design makes it possible to create more scalable and stable devices. To use them in practice, one has to reconstruct the whole device model taking the manufacturing errors into account. The inability to address individual interferometer elements complicates the reconstruction problem. A naive approach is to train the model via some complex optimization procedure. A faster optimization-free algorithm has been recently proposed [Opt. Express 31, 16729 (2023)]. However, it requires the full transfer matrix tomography while a more practical setup measures only the fields intensities at the interferometer output. In this paper, we propose the modification of the fast algorithm, which uses additional set of interferometer configurations in order to reconstruct the model in the case of intensity-only measurements. We show that it performs slightly worse than the original fast algorithm but it is more practical and still does not require intensive numerical optimization

Diffusion mass transfer in ionic materials under intense electron irradiation

The results of studies on the impact of an electron beam with the energy of 1-2 MeV on diffusion processes in materials with ionic bonds are presented in the paper. Used electron beam intensity is allowed to provide heating of the material to temperatures of 1600 K. Diffusion of Na, Mg, Al ions into single crystals KBr in the temperature range 573-883 K, Al ions in the NiO-AlO system at 1373-1573 K, was studied. Diffusion annealing carried out under thermal and radiation-thermal heating of the samples. Then diffusion coefficients were determined. It was found stimulating action of irradiation on diffusion processes of Mg, Al ions in Kbr and Al ions in the NiO-Al[2]O[3] system, which consists in increasing the diffusion coefficients at radiation-thermal annealing. The observed effect is achieved by increasing the effective rate of diffusion jumps