Laser-controlled local magnetic field with semiconductor quantum rings.pdf
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Laser-controlled local magnetic field with semiconductor quantum
rings
Yuriy V. Pershin? and Carlo Piermarocchi
Department of Physics and Astronomy,
Michigan State University, East Lansing, Michigan 48824
(Dated: February 2, 2008)
Abstract
We analize theoretically the dynamics of N electrons localized in a semiconductor quantum ring
under a train of phase-locked infrared laser pulses. The pulse sequence is designed to control the
total angular momentum of the electrons. The quantum ring can be put in states characterized
by strong currents. The local magnetic field created by these currents can be used for a selective
quantum control of single spins in semiconductor systems.
PACS numbers: 73.23.Ra, 78.67.-n
?Electronic address: pershin@pa.msu.edu
1
The quantum control by trains of phase-locked laser pulses is a powerful and intuitive
technique that has been applied to many atomic and molecular systems. It has been success-
fully employed in controlling the angular momentum of Rydberg electrons and molecular
wavepackets [1], and it was the key technique in the creation of Schro?diger cat’s states in
Rydberg atoms [2]. Semiconductor quantum dots and rings are artificial atoms with en-
ergy levels that can be engineered, and the realization of optical control in these systems is
particularly appealing for quantum device applications.
In this paper we propose a scheme involving phase-locked infrared pulses to control the
total angular momentum of N electrons in a quantum ring. This implies that a strong
current can be generated in the ring. The latter can be exploited to generate and control
a local magnetic field in spin-based quantum computers [3, 4]. A possible application of
the radiation-induced currents to single spin control is shown in Fig. 1(a). A spin, provided
e.g. by a magnetic impurity, is embedded at the center or on top of a narrow quantum
ring a
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