26 July 2001 Behavior of a persistent current qubit in a time-dependent electromagnetic field
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Abstract
This paper considers the behavior of a model persistent current qubit in the presence of a time-dependent electromagnetic field. A semi-classical approximation for the electromagnetic field is used to solve the time- dependent Schrodinger equation (TDSE) for the qubit, which is treated as a macroscopic quantum object. The qubit is describe3d by a Hamiltonian involving the enclosed magnetic flux (Phi) and the electric displacement flux Q, which obey the quantum mechanical commutation relation. The paper includes a brief summary of recent work on quantum mechanical coherence in persistent current circuits, and the solution of the TDSE in superconducting rings. Of particular interest is the emergence of strongly non-perturbative behavior that corresponds to transitions between the energy levels of the qubit. These transitions are due to the strong coupling between the electromagnetic fields and the superconducting condensate and can appear at frequencies predicted by conventional methods based on perturbations around the energy eigenstate of the time-independent system. The relevance of these non-perturbative processes to the operation of quantum logic gates based on superconducting circuits and the effect of the resultant non linearities on the environmental degrees of freedom coupled to the qubit are considered.
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Jason F. Ralph, Jason F. Ralph, Terrence D. Clark, Terrence D. Clark, Mark J. Everitt, Mark J. Everitt, Peter Steiffell, Peter Steiffell, Apostolos Vourdas, Apostolos Vourdas, Robert J. Prance, Robert J. Prance, Helen Prance, Helen Prance, "Behavior of a persistent current qubit in a time-dependent electromagnetic field", Proc. SPIE 4386, Photonic and Quantum Technologies for Aerospace Applications III, (26 July 2001); doi: 10.1117/12.434218; https://doi.org/10.1117/12.434218
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