Abstract:The control of single spins in solids is a key but challenging step for any
spin-based solid-state quantumcomputing device. Thanks to their expected long
coherence time, localized spins on magnetic atoms in a semiconductor host could
be an interesting media to store quantum information in the solid state. Optical
probing and control of the spin of individual or pairs of Manganese (Mn) atoms
(S = 5/2) have been obtained in II-VI and IIIV semiconductor quantum dots during
the last years. In this paper, we review recently developed optical control
experiments of the spin of an individual Mn atoms in II-VI semiconductor
self-assembled or strain-free quantum dots (QDs).We first show that the fine
structure of the Mn atom and especially a strained induced magnetic anisotropy
is the main parameter controlling the spin memory of the magnetic atom at zero
magnetic field. We then demonstrate that the energy of any spin state of a Mn
atom or pairs of Mn atom can be independently tuned by using the optical Stark
effect induced by a resonant laser field. The strong coupling with the resonant
laser field modifies the Mn fine structure and consequently its dynamics.We then
describe the spin dynamics of a Mn atom under this strong resonant optical
excitation. In addition to standard optical pumping expected for a resonant
excitation, we show that the Mn spin population can be trapped in the state
which is resonantly excited. This effect is modeled considering the coherent
spin dynamics of the coupled electronic and nuclear spin of the Mn atom
optically dressed by a resonant laser field. Finally, we discuss the spin
dynamics of a Mn atom in strain-free QDs and show that these structures should
permit a fast optical coherent control of an individual Mn spin.
Entanglement on macroscopic scales in a resonant-laser-field-excited atomic ensemble
