Quantum register based on structured diamond waveguide with NV centers

We propose a scheme of quantum information processing with NV-centers embedded inside diamond nanostructure. Single NV-center placed in the cavity plays role of an electron spin qubit which evolution is controlled by microwave pulses. Besides, it couples to the cavity field via optical photon exchange. In their turn, neighbor cavities are coupled to each other through the photon hopping to form a bus waveguide mode. This waveguide mode overlaps with all NV-centers. Entanglement between distant centers is organized by appropriate tuning of their optical frequency relative to the waveguide frequency via electrostatic control without lasers. We describe the controlled-Z operation that is by one order of magnitude faster than in off-resonant laser-assisted schemes proposed earlier. Spectral characteristics of the one-dimensional chain of microdisks are calculated by means of numerical modeling, using the approach analogous to the tight-binding approximation in the solid-state physics. The data obtained allow to optimize the geometry of the microdisk array for the effective implementation of quantum operations.Comment: to be published in Proc. of SPI

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

All-quantum simulation of an ultra-small SOI MOSFET

The all-quantum program for 3D simulation of an ultra-thin body SOI MOSFET is overviewed. It is based on Landauer-Buttiker approach to calculate current. The necessary transmission coefficients are acquired from the self-consistent solution of Schrödinger equation. The latter is stabilized with the help of expanding the wave function over the modes of transversal quantization inside the transistor channel. The program also contains a domain for onedimensional classical ballistics intended for calculation of the initial state for subsequent all-quantum simulation. This is a significant point of our approach as the straightforward procedure of the self-consistent solution of Schrödinger equation from the very beginning is diverging or, at least, extremely time-consuming. The main goal of all-quantum simulation is to clarify the impact of interference on charged impurities and quantum reflection from self-consistent potential on I-V curve reproducibility for different rand omly doped transistors in a circuit. The 10nm technology node tri-gate (wrapped channel) structure with 2nm silicon body was used in simulation. 20 discrete impurities were dispersed by the source and drain contacts to imitate the same doping. The most important feature we demonstrate is a smoothness of I-V curves in spite of beforehand apprehension. The next peculiarity we came across was that the current spanned within 10% for different discrete impurity realizations. These results manifest that the reproducibility of nanotransistors could be fairly good to make ultra-large integrated circuits still feasible. We have also made a comparison with simulations based on drift-diffusion model