Various Combinations Of Polarization Research Articles

Single-photon heralded two-qubit unitary gates for pairs of nitrogen-vacancy centers in diamond

The implementation of a high-fidelity two-qubit quantum logic gate remains an outstanding challenge for isolated solid-state qubits such as nitrogen-vacancy (NV) centers in diamond. In this work, we show that by driving pairs of NV centers to undergo photon scattering processes that flip their qubit states simultaneously, we can achieve a unitary two-qubit gate conditioned upon a single photon-detection event. Further, by exploiting quantum interference between the optical transitions of the NV centers' electronic states, we realize the existence of two special drive frequencies: a ``magic'' point where the spin-preserving elastic scattering rates are suppressed and a ``balanced'' point where the state-flipping scattering rates are equal. We analyzed four different gate operation schemes that utilize these two special drive frequencies, and various combinations of polarizations in the drive and collection paths. Our theoretical and numerical calculations show that the gate fidelity can be as high as 98%. The proposed unitary gate, combined with available single-qubit unitary operations, forms a universal gate set for quantum computing.

Special features of radio control link for energy efficient LED light sources

The aim of the study is to reveal the special features of radio control link model in LR-WPAN under operating conditions of interference of the reflected and the line-of-sight component and to evaluate the radio link's range of positive light source control. The results of development and practical implementation of controlled spectrally tunable light emitting diode (LED) light sources with ISM- and ZigBee (IEEE 802.15.04)-based radio frequency transceivers are presented. A software application developed in LabVIEW simulation of a radio control link for light sources and used for evaluating the radio control link's range of various combinations of polarization of transmitting and receiving antennas has been discussed. It was established and experimentally verified that the received energy was able to be computed using the two-ray model: a line-of-sight ray and the reflected one. This approach is simpler as compared to cellular networks in which multiple reflections from various objects result in multi-path propagation without line-of-sight component.

Resummation for polarized semi-inclusive deep-inelastic scattering at small transverse momentum

We study the transverse-momentum distribution of hadrons produced in semi-inclusive deep-inelastic scattering (SIDIS). We consider cross sections for various combinations of polarizations of the initial lepton and nucleon or the produced hadron, for which we perform the resummation of large double-logarithmic perturbative corrections arising at small transverse momentum. We present phenomenological results for the processes l p → l π X with longitudinally polarized leptons and protons. We discuss the impact of the perturbative resummation and of estimated non-perturbative contributions on the corresponding cross sections and their spin asymmetry. Our results should be relevant for ongoing studies in the COMPASS experiment at CERN, and for future experiments at the proposed eRHIC collider at BNL.

Polarimetric Study of Degenerate Four-wave Mixing with Folded Boxcars Geometry in Isotropic Medium

Abstract We obtain expressions for the third-order nonlinearities responsible for degenerate four-wave mixing (DFWM) with folded boxcar geometry in an isotropic medium. The effects of various combinations of polarizations of the three input beams are also discussed.