| 1. |
- Allahverdyan, A, et al.
(författare)
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Brownian entanglement
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72, s. 032102-
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Azimi Mousolou, Vahid, et al.
(författare)
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Non-Abelian geometric phases in a system of coupled quantum bits
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 89:2, s. 022117-
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Tidskriftsartikel (refereegranskat)abstract
- A common strategy to measure the Abelian geometric phase for a qubit is to let it evolve along an `orange slice' shaped path connecting two antipodal points on the Bloch sphere by two different semi-great circles. Since the dynamical phases vanish for such paths, this allows for direct interference measurement of the geometric phase. Here, we generalize the orange slice setting to the non-Abelian case. The proposed method to measure the non-Abelian geometric phase can be implemented in a cyclic chain of four qubits with controllable nearest-neighbor interactions.
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| 3. |
- Azimi Mousolou, Vahid, et al.
(författare)
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Non-Abelian quantum holonomy of hydrogen-like atoms
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 84:3
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Tidskriftsartikel (refereegranskat)abstract
- We study the Uhlmann holonomy [Rep. Math. Phys. 24, 229 (1986)] of quantum states for hydrogen-like atoms, where the intrinsic spin and orbital angular momentum are coupled by the spin-orbit interaction and subject to a slowly varying magnetic field. We show that the holonomy for the orbital angular momentum and spin subsystems is non-Abelian, while the holonomy of the whole system is Abelian. Quantum entanglement in the states of the whole system is crucially related to the non-Abelian gauge structure of the subsystems. We analyze the phase of the Wilson loop variable associated with the Uhlmann holonomy, and find a relation between the phase of the whole system with corresponding marginal phases. Based on the result for the model system we provide evidence that the phase of the Wilson loop variable and the mixed-state geometric phase [Phys. Rev. Lett. 85, 2845 (2000)] are in general inequivalent.
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| 4. |
- Azimi Mousolou, Vahid, et al.
(författare)
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Unifying Geometric Entanglement and Geometric Phase in a Quantum Phase Transition
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 88:1, s. 012310-
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Tidskriftsartikel (refereegranskat)abstract
- Geometric measure of entanglement and geometric phase have recently been used to analyze quantum phase transition in the XY spin chain. We unify these two approaches by showing that the geometric entanglement and the geometric phase are respectively the real and imaginary parts of a complex-valued geometric entanglement, which can be investigated in typical quantum interferometry experiments. We argue that the singular behavior of the complex-value geometric entanglement at a quantum critical point is a characteristic of any quantum phase transition, by showing that the underlying mechanism is the occurrence of level crossings associated with the underlying Hamiltonian.
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| 5. |
- Hansson, Anders, et al.
(författare)
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Effect of bending and vacancies on the conductance of carbon nanotubes
- 2000
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 62:11, s. 7639-7644
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Tidskriftsartikel (refereegranskat)abstract
- Electron transport through nanotubes is studied theoretically using the Landauer formalism. The studies are carried out for finite metallic nanotubes that bridge two contacts pads. The current is observed to increase stepwise with the applied voltage. Each step corresponds to resonance tunneling including one single-particle eigenstate of the nanotube. Moderate bending of the nanotube results in a shift of the single-particle levels but the overall current remains essentially unaffected. For large bending, however, the pi electron system becomes more disturbed, which introduces backscattering and a marked decrease in the conductivity along the tube. A single carbon vacancy in the nanotube is shown to have very small effect on the conductivity in the center of the metallic band whereas, by increasing the defect concentration the conductivity decreases in the same way as for the strongly bent tubes.
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