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Geometric Phase for Analytically Solvable Driven Time-Dependent Two-Level Quantum Systems

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Mendaš I., Burić N., Popović D., Prvanović S., Radonjić M.

Acta Physica Polonica A

2014

vol. 126

issue 3

670-673

Geometric phase for novel analytical solutions (Barnes and Das Sarma) of time-dependent two-level quantum systems is discussed, specifically for a general single-axis driving term, which is represented by a function J(t) in the Hamiltonian, and its corresponding evolution operator. It is demonstrated how general results for corresponding phases (total, dynamic and geometric) can be obtained. Using a specific case, it was found that over time in which the driving field is appreciably different from zero, the corresponding geometric phase changes (in the specific example by Δ β ≈ 0.8 radians) thus enabling detection. The results are relevant to qubit control and to quantum computing applications.

Quantum Hall Ferromagnet in Magnetically-Doped Quantum Wells

73%

Andrearczyk T., Jaroszyński J., Wróbel J., Karczewski G., Wojtowicz T., Papis E., Kamińska E., Piotrowska A., Popović D., Dietl T.

Acta Physica Polonica A

2003

vol. 104

issue 2

93-102

The article reviews our recent studies on quantum Hall ferromagnetism in diluted magnetic semiconductors. We carried out magnetoresistance studies on modulation-doped, gated heterostructures of (Cd,Mn)Te/(Cd,Mg)Te:I. We put into evidence the formation of Ising quantum Hall ferromagnet with Curie temperature T_C as high as 2 K. Quantum Hall ferromagnetism is manifested by anomalous magnetoresistance maxima. Moreover, magnitude of these spikes depends dramatically on the history of the sample, shows hysteresis when either magnetic field or gate voltage are swept, stretched-exponential time evolution characteristic of glassy systems, and strong Barkhausen noise. Our study suggests that these metastabilities stem from the slow dynamics of ferromagnetic domains.

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2 Acta Physica Polonica A

1 2014

1 2003

2 Popović D.

1 Andrearczyk T.

1 Burić N.

1 Dietl T.

1 Jaroszyński J.

1 Kamińska E.

1 Karczewski G.

1 Mendaš I.

1 Papis E.

1 Piotrowska A.

1 Prvanović S.

1 Radonjić M.

1 Wojtowicz T.

1 Wróbel J.

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Geometric Phase for Analytically Solvable Driven Time-Dependent Two-Level Quantum Systems

Quantum Hall Ferromagnet in Magnetically-Doped Quantum Wells