Cold Atoms
Department of Molecular and Optical Physics - University of Freiburg, Germany.

Phase control and diagnostic of quantum mechanical superposition states
C. Basler, K. Reininger, F. Meinert, P. N. Ghosh, and H. Helm
Department of Molecular and Optical Physics, University of Freiburg, Stefan-Meier-Strasse 19, 79104 Freiburg, Germany

Phys. Rev. A 87, 013430 (2013) [8 pages]


We report experiments on the control of the phase η in quantum mechanical superposition states which emerge in electromagnetically induced transparency, | ψ ⟩ = ( | 1 ⟩ + e | 2 ⟩ ) / √2 . We interpret our findings in terms of the measurement role that spontaneous emission and the light fields play in selecting the optically dark and bright superpositions. A phase-switching tool is introduced which enables the rapid measurement of the absolute depth of the dark-state minimum and its absolute position on the frequency scale without detuning the lasers. The phase-switching technique allows one to determine the relative phase η in an ensemble of quantum mechanical superposition states of a Λ system in a minimally invasive way.

©2013 American Physical Society

DOI: 10.1103/PhysRevA.87.013430
PACS: 32.80.Qk, 42.50.Gy, 32.30.-r