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Floquet formulation for the investigation of multiphoton quantum interference in a superconducting qubit driven by a strong ac field
SangKil Son, Siyuan Han, and ShihI Chu
Phys. Rev. A 79, 032301 (2009) [BibTeX][pdf]doi:10.1103/PhysRevA.79.032301
We present a Floquet treatment of multiphoton quantum interference in a strongly driven superconducting flux qubit. The periodically timedependent Schrödinger equation can be reduced to an equivalent timeindependent infinitedimensional Floquet matrix eigenvalue problem. For resonant or nearly resonant multiphoton transitions, we extend the generalized Van Vleck (GVV) nearly degenerate highorder perturbation theory for the treatment of the Floquet Hamiltonian, allowing the reduction of the infinitedimensional Floquet matrix to an N×N effective Hamiltonian, where N is the number of eigenstates under consideration. The GVV approach allows accurate treatment of ac Stark shift, power broadening, timedependent and timeaveraged transition probability, etc., well beyond the rotating wave approximation. We extend the Floquet and GVV approaches for numerical and analytical studies of the multiphoton resonance processes and quantum interference phenomena for the superconducting flux qubit system (N=2) driven by intense ac fields. Tags: Floquet,
qubit,
SQUID,
twolevel,
quantum interference,
strongfield,
RWA,
GVV,
KU
