3 research outputs found
Proposal for generating and detecting multi-qubit GHZ states in circuit QED
We propose methods for the preparation and entanglement detection of
multi-qubit GHZ states in circuit quantum electrodynamics. Using quantum
trajectory simulations appropriate for the situation of a weak continuous
measurement, we show that the joint dispersive readout of several qubits can be
utilized for the probabilistic production of high-fidelity GHZ states. When
employing a nonlinear filter on the recorded homodyne signal, the selected
states are found to exhibit values of the Bell-Mermin operator exceeding 2
under realistic conditions. We discuss the potential of the dispersive readout
to demonstrate a violation of the Mermin bound, and present a measurement
scheme avoiding the necessity for full detector tomography.Comment: 9 pages, 5 figure
Parametric amplification with weak-link nonlinearity in superconducting microresonators
Nonlinear kinetic inductance in a high Q superconducting coplanar waveguide
microresonator can cause a bifurcation of the resonance curve. Near the
critical pumping power and frequency for bifurcation, large parametric gain is
observed for signals in the frequency band near resonance. We show experimental
results on signal and intermodulation gain which are well described by a theory
of the parametric amplification based on a Kerr nonlinearity. Phase dependent
gain, or signal squeezing, is verified with a homodyne detection scheme.Comment: Submitted to Physica Scripta, topical issue: Nobel Symposium on
Quantum Bits, 2009. 10 pages, 5 figures. Version 2 contains a few new
sentences about the current-phase relation of weak link