Quasieigenstate coalescence in an atom-cavity quantum composite.
We report the first direct observation of an exceptional point (EP) in an open quantum composite of a single atom and a high-Q cavity mode. The atom-cavity coupling constant was made a continuous variable by utilizing the multisublevel nature of a single rubidium atom when it is optimally coupled to the cavity mode. The spectroscopic properties of quasieigenstates of the atom-cavity composite were experimentally investigated near the EP. Branch-point singularity of quasieigenenergies was observed and its 4pi symmetry was demonstrated. Consequently, the cavity transmission at the quasieigenstate was observed to exhibit a critical behavior at the EP.
Choi
Youngwoon
Y
School of Physics and Astronomy, Seoul National University, Seoul, 151-747, Korea.
Kang
Sungsam
S
Lim
Sooin
S
Kim
Wookrae
W
Kim
Jung-Ryul
JR
Lee
Jai-Hyung
JH
An
Kyungwon
K