title: Quantum entanglement and spin control in silicon nanocrystal.
abstract: Selective coherence control and electrically mediated exchange coupling of single electron spin between triplet and singlet states using numerically derived optimal control of proton pulses is demonstrated. We obtained spatial confinement below size of the Bohr radius for proton spin chain FWHM. Precise manipulation of individual spins and polarization of electron spin states are analyzed via proton induced emission and controlled population of energy shells in pure (29)Si nanocrystal. Entangled quantum states of channeled proton trajectories are mapped in transverse and angular phase space of (29)Si <100> axial channel alignment in order to avoid transversal excitations. Proton density and proton energy as impact parameter functions are characterized in single particle density matrix via discretization of diagonal and nearest off-diagonal elements. We combined high field and low densities (1 MeV/92 nm) to create inseparable quantum state by superimposing the hyperpolarizationed proton spin chain with electron spin of (29)Si. Quantum discretization of density of states (DOS) was performed by the Monte Carlo simulation method using numerical solutions of proton equations of motion. Distribution of gaussian coherent states is obtained by continuous modulation of individual spin phase and amplitude. Obtained results allow precise engineering and faithful mapping of spin states. This would provide the effective quantum key distribution (QKD) and transmission of quantum information over remote distances between quantum memory centers for scalable quantum communication network. Furthermore, obtained results give insights in application of channeled protons subatomic microscopy as a complete versatile scanning-probe system capable of both quantum engineering of charged particle states and characterization of quantum states below diffraction limit linear and in-depth resolution.PACS NUMBERS: 03.65.Ud, 03.67.Bg, 61.85.+p, 67.30.hj.
authors.affiliation: Faculty of Physics, Department of Condensed Matter Physics, University in Belgrade, Belgrade, Serbia. bervesn@gmail.com
authors.forename: Vesna
authors.initials: V
authors.lastname: Berec
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation* / Q000379:methods*; D011522:Protons; D011789:Quantum Theory; D012825:Silicon / Q000737:chemistry*; D013113:Spin Labels
chemical_list: D011522:Protons; D013113:Spin Labels; D012825:Silicon