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Quantum control theory and applications: A survey
 IET Control Theory & Applications
, 2010
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Decoherencefree subspaces and subsystems
 In Irreversible Quantum Dynamics, Benatti , F., Floreanini, R. (Eds.), 83120 (Springer Lecture Notes in Physics
, 2003
"... Abstract. Decoherence is the phenomenon of nonunitary dynamics that arises as a consequence of coupling between a system and its environment. It has important harmful implications for quantum information processing, and various solutions to the problem have been proposed. Here we provide a detailed ..."
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Abstract. Decoherence is the phenomenon of nonunitary dynamics that arises as a consequence of coupling between a system and its environment. It has important harmful implications for quantum information processing, and various solutions to the problem have been proposed. Here we provide a detailed a review of the theory of decoherencefree subspaces and subsystems, focusing on their usefulness for preservation of quantum information. 1
Modeling and Control of Quantum Systems: An introduction
"... The scope of this work is to provide a selfcontained introduction to a selection of basic theoretical aspects in the modeling and control of quantum mechanical systems, as well ..."
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The scope of this work is to provide a selfcontained introduction to a selection of basic theoretical aspects in the modeling and control of quantum mechanical systems, as well
Models of Quantum Computers and Decoherence Problem, ePrint archive http://xxx.lanl.gov/ quantph /9902055
 Proc. of the International Conference on Quantum Information, Meijo Univ. Nagoya
, 1997
"... Mathematical models of quantum computers such as a multidimensional quantum Turing machine and quantum circuits are described and its relations with lattice spin models are discussed. One of the main open problems one has to solve if one wants to build a quantum computer is the decoherence due to th ..."
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Mathematical models of quantum computers such as a multidimensional quantum Turing machine and quantum circuits are described and its relations with lattice spin models are discussed. One of the main open problems one has to solve if one wants to build a quantum computer is the decoherence due to the coupling with the environment. We propose a possible solution of this problem by using a control of parameters of the system. This proposal is based on the analysis of the spinboson Hamiltonian performed in the stochastic limit approximation. Invited talk at the International Conference on Quantum Information, Meijo University, Nagoya, 48 Nov.1997. To be published in Proc. of the Conference
Ultrafast optical rotations of electron spins in quantum dots
, 2009
"... Coherent manipulation of quantum bits (qubits) on time scales much shorter than the coherence time 1,2 is a key prerequisite for quantum information processing. Electron spins in quantum dots (QDs) are particularly attractive for implementations of qubits. Efficient optical methods for initializatio ..."
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Coherent manipulation of quantum bits (qubits) on time scales much shorter than the coherence time 1,2 is a key prerequisite for quantum information processing. Electron spins in quantum dots (QDs) are particularly attractive for implementations of qubits. Efficient optical methods for initialization and readout of spins have been developed in recent years 3,4. Spin coherence times in the microsecond range have been demonstrated 5, so that spin control by picosecond optical pulses would be highly desirable. Then a large number of spin rotations could be performed while coherence is maintained. A major remaining challenge is demonstration of such rotations with high fidelity. Here we use an ensemble of QD electron spins focused into a small number of precession modes about a magnetic field by periodic optical pumping. We demonstrate ultrafast optical rotations of spins about arbitrary axes on a picosecond time scale using laser pulses as control fields. Spin rotations have been obtained for gated GaAs transport QDs using rf fields, but such manipulations are slow with times comparable to the spin coherence time 6. Fast optical rotation operations on spins in QDs are being sought actively, but progress to date has been limited. In an alloptical experiment on shallow interface fluctuation QDs, weak confinement precluded full unitary spin rotations 7. Evidence for spin rotations was reported for a single GaAs interface fluctuation quantum dot using very intense optical excitation needed for spins to be rotated by precession about the effective laser magnetic field 8. Very recently more convincing rotations in a single InAs selforganized QD were reported 9. This work on single QDs