Multiphoton transitions in a macroscopic quantum two-state system.
We have observed multiphoton transitions between two macroscopic quantum-mechanical superposition states formed by two opposite circulating currents in a superconducting loop with three Josephson junctions. Resonant peaks and dips of up to three-photon transitions were observed in spectroscopic measurements when the system was irradiated with a strong rf-photon field. The widths of the multiphoton absorption dips are shown to scale with the Bessel functions in agreement with theoretical predictions derived from the Bloch equation or from a spin-boson model.
NTT Basic Research Laboratories, NTT Corporation, Kanagawa 243-0198, Japan.
S
S
Saito
M
M
Thorwart
H
H
Tanaka
M
M
Ueda
H
H
Nakano
K
K
Semba
H
H
Takayanagi