Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 30: Poster II

Q 30.48: Poster

Tuesday, March 3, 2009, 16:30–19:00, VMP 9 Poster

Quantum interference and entanglement in flux qubits — •Keyu Xia, Mihai Macovei, Jörg Evers, and Christoph H. Keitel — MPI für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg

Superconducting qubits, and in particular flux qubits, are promising candidates for a number of applications in quantum information science. In this work, we discuss different aspects of quantum interference and entanglement in flux qubits.

First, we propose a robust coherent control scheme for the creation of Bell states of two coupled flux qubits via a dynamic control of the qubit transition frequency near their optimal point [1]. Using this technique, an arbitrary superposition of different Bell states composed of the collective ground and excited states can be achieved. The preparation is robust against imperfections in the driving fields.

Secondly, we discuss ground state cooling of a nanomechanical resonator. Our approach is to make use of quantum interference via coupling it to a flux qubit. This flux qubit is modeled as a Λ−type three-level system, enabling the use of electromagnetically induced transparency to implement the ground state cooling. We find ground state occupations of more than 90% in the steady state. Interestingly, compared to sideband cooling of the resonator, a contribution proportional to the initial phonon number of the nanomechanical resonator is suppressed by a factor of the detuning.

[1] K. Xia, M. Macovei, J. Evers, and C. H. Keitel, arXiv:0810.2453