| 1. |
- Saxena, Ruchi, et al.
(författare)
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Electronic confinement of surface states in a topological insulator nanowire
- 2022
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 106:3
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the confinement of electronic surface states in a model of a topological insulator nanowire. Spin-momentum locking in the surface states reduces unwanted backscattering in the presence of nonmagnetic disorder and is known to counteract localization for certain values of magnetic flux threading the wire. We show that intentional backscattering can be induced for a range of conditions in the presence of a nanowire constriction. We propose a geometry for a nanowire that involves two constrictions and show that these regions form effective barriers that allow for the formation of a quantum dot. We analyze the zero-temperature noninteracting electronic transport through the device using the Landauer-Büttiker approach and show how externally applied magnetic flux parallel to the nanowire and electrostatic gates can be used to control the spectrum of the quantum dot and the electronic transport through the surface states of the model device.
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| 2. |
- Bishop, Lev S., et al.
(författare)
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Proposal for generating and detecting multi-qubit GHZ states in circuit QED
- 2009
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 073040-
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Tidskriftsartikel (refereegranskat)abstract
- We propose methods for the preparation and entanglement detectionof multi-qubit Greenberger–Horne–Zeilinger (GHZ) states in circuit quantumelectrodynamics. Using quantum trajectory simulations appropriate for thesituation of a weak continuous measurement, we show that the joint dispersivereadout of several qubits can be utilized for the probabilistic production ofhigh-fidelity GHZ states. When employing a nonlinear filter on the recordedhomodyne signal, the selected states are found to exhibit values of theBell–Mermin operator exceeding 2 under realistic conditions. We discuss thepotential of the dispersive readout to demonstrate a violation of the Merminbound, and present a measurement scheme avoiding the necessity for fulldetector tomography.
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| 3. |
- Brookes, Paul, et al.
(författare)
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Critical slowing down in circuit quantum electrodynamics
- 2021
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Ingår i: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:21
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Tidskriftsartikel (refereegranskat)abstract
- Critical slowing down of the time it takes a system to reach equilibrium is a key signature of bistability in dissipative first-order phase transitions. Understanding and characterizing this process can shed light on the underlying many-body dynamics that occur close to such a transition. Here, we explore the rich quantum activation dynamics and the appearance of critical slowing down in an engineered superconducting quantum circuit. Specifically, we investigate the intermediate bistable regime of the generalized Jaynes-Cummings Hamiltonian (GJC), realized by a circuit quantum electrodynamics (cQED) system consisting of a transmon qubit coupled to a microwave cavity. We find a previously unidentified regime of quantum activation in which the critical slowing down reaches saturation and, by comparing our experimental results with a range of models, we shed light on the fundamental role played by the qubit in this regime.
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