| 1. |
- 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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| 2. |
- Chakraborty, P. B., et al.
(författare)
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Theory of the magnetic phase diagram of LiHoF4
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:14
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Tidskriftsartikel (refereegranskat)abstract
- The properties of LiHoF4 are believed to be well described by a long-range dipolar Ising model. We go beyond mean-field theory and calculate the phase diagram of the Ising model in a transverse field using a quantum Monte Carlo method. The relevant Ising degrees of freedom are obtained using a nonperturbative projection onto the low-lying crystal-field eigenstates. We explicitly take the domain structure into account, and the strength of the near-neighbor exchange interaction is obtained as a fitting parameter. The on-site hyperfine interaction is approximately taken into account through a renormalization of the transverse applied magnetic field. Finally, we propose a spectroscopy experiment to precisely measure the most important parameter controlling the location of the phase boundary.
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| 3. |
- Chow, J.M., et al.
(författare)
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Randomized benchmarking and process tomography for gate errors in a solid-state qubit
- 2009
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 102:9
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of single-qubit gate errors for a superconducting qubit. Results from quantum process tomography and randomized benchmarking are compared with gate errors obtained from a double pulse experiment. Randomized benchmarking reveals a minimum average gate error of 1.1±0.3% and a simple exponential dependence of fidelity on the number of gates. It shows that the limits on gate fidelity are primarily imposed by qubit decoherence, in agreement with theory.
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| 4. |
- Henelius, Patrik, et al.
(författare)
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Monte Carlo study of a two-dimensional quantum ferromagnet
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:1, s. 364-374
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Tidskriftsartikel (refereegranskat)abstract
- We present quantum Monte Carlo results for the field and temperature dependence of the magnetization and the spin lattice relaxation rate 1/T-1 of a two-dimensional S = 1/2 quantum Heisenberg ferromagnet. The Monte Carlo method, which yields results free of systematic errors, is described in detail. The high accuracy of the calculated magnetization allows for stringent tests of recent approximate analytical calculations. We also compare our results with recent experimental data for a nu = 1 quantum Hall ferromagnet, which is expected to be well described by the Heisenberg model. The dynamic response function needed to extract 1/T-1 is obtained using maximum-entropy analytic continuation of the corresponding imaginary-time dependent correlation function. We discuss the reliability of this approach.
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| 5. |
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