Search results for "Spin quantum number"
showing 10 items of 14 documents
Entanglement generation between two spin-s magnetic impurities in a solid via electron scattering
2009
Abstract We present a scheme for generating entanglement between two magnetic impurities in a solid-state system via electron scattering. The scheme applies to impurities of arbitrary quantum spin number. We show that resonance conditions yield generation of a maximally entangled state of the impurities' spins, regardless of the value of the electron–impurity coupling constant and the impurity spin quantum number. The mechanism behind the scheme is explained in terms of resonance-induced selection rules.
Transfer of arbitrary two-qubit states via a spin chain
2015
We investigate the fidelity of the quantum state transfer (QST) of two qubits by means of an arbitrary spin-1/2 network, on a lattice of any dimensionality. Under the assumptions that the network Hamiltonian preserves the magnetization and that a fully polarized initial state is taken for the lattice, we obtain a general formula for the average fidelity of the two qubits QST, linking it to the one- and two-particle transfer amplitudes of the spin-excitations among the sites of the lattice. We then apply this formalism to a 1D spin chain with XX-Heisenberg type nearest-neighbour interactions adopting a protocol that is a generalization of the single qubit one proposed in Ref. [Phys. Rev. A 8…
Magnetic field dependence of quantum dot ground states
2008
We study the ground states of a planar quantum dot with N = 5,6,7 electrons, in the presence of a perpendicular magnetic field. Using a spatially unrestricted Hartree Fock technique followed by spin and angular momentum symmetry restoration, chemical potentials are calculated and transitions between different ground states are identified. A spin blockade in the 6 -> 7 transition is found. The structure of the quantum dot wave functions is illustrated by their electron densities. (c) 2007 Elsevier B.V. All rights reserved.
Low-energy spectrum and finite temperature properties of quantum rings
2002
Recently it was demonstrated that the rotational and vibrational spectra of quantum rings containing few electrons can be described quantitatively by an effective spin-Hamiltonian combined with rigid center-of-mass rotation and internal vibrations of localized electrons. We use this model Hamiltonian to study the quantum rings at finite temperatures and in presence of a nonzero magnetic field. Total spin, angular momentum and pair correlation show similar phase diagram which can be understood with help of the rotational spectrum of the ring.
Spin projected unrestricted Hartree-Fock ground states for harmonic quantum dots
2008
We report results for the ground state energies and wave functions obtained by projecting spatially unrestricted Hartree Fock states to eigenstates of the total spin and the angular momentum for harmonic quantum dots with $N\leq 12$ interacting electrons including a magnetic field states with the correct spatial and spin symmetries have lower energies than those obtained by the unrestricted method. The chemical potential as a function of a perpendicular magnetic field is obtained. Signature of an intrinsic spin blockade effect is found.
Alignment-orientation transition at optical excitation of molecules in magnetic field
1995
Abstract Angular momentum alignment-orientation transition is analyzed for the ground state of diatomic or linear molecules subjected to the dynamic Stark effect. Analytical expressions are derived for the orientation value. It is shown that, first, orientation of angular momenta resulting from the action of the dynamic Stark effect is a nonlinear process which depends quadratically on the intensity of the irradiating light; second, it is a quantum effect and disappears for the states with large angular momenta; and, third, it occurs only in the presence of an external magnetic field.
Non-Markovian dynamics of a single electron spin coupled to a nuclear spin bath
2008
We apply the time-convolutionless (TCL) projection operator technique to the model of a central spin which is coupled to a spin bath via nonuniform Heisenberg interaction. The second-order results of the TCL method for the coherences and populations of the central spin are determined analytically and compared with numerical simulations of the full von Neumann equation of the total system. The TCL approach is found to yield an excellent approximation in the strong field regime for the description of both the short-time dynamics and the long time behavior.
Rising time of entanglement between scattering spins,
2009
We investigate the time evolution of entanglement in a process where a mobile particle is scattered by static spins. We show that entanglement increases monotonically during a transient and then saturates to a steady-state value. For a quasi-monochromatic mobile particle, the transient time depends only on the group-velocity and width of the incoming wavepacket and is insensitive to the interaction strength and spin-number of the scattering particles. These features do not depend on the interaction model and can be seen in various physical settings.
Electronic and magnetic structure of artificial atoms
1999
The concept of shell structure has been found useful in the description of semiconductor quantum dots, which today can be made so small that they contain less than 20 electrons. We review the experimental discovery of magic numbers and spin alignment following Hund’s rules in the addition spectra of vertical quantum dots, and show that these results compare well to model calculations within spin density functional theory. We further discuss the occurrence of spin density waves in quantum dots and quantum wires. For deformable two-dimensional quantum dots (for example, jellium clusters on surfaces), we study the interplay between Hund’s rules and Jahn–Teller deformations and investigate the …
Hund's Rules and Spin Density Waves in Quantum Dots
1997
Spin density functional theory is used to calculate the ground state electronic structures of circular parabolic quantum dots. We find that such dots either have a spin configuration determined by Hund's rule or make a spin-density-wave-like state with zero total spin. The dependence of the spin-density-wave amplitudes on the density of the two-dimensional electron gas is studied.