Quasieigenstate coalescence in an atom-cavity quantum composite

Youngwoon Choi, Sungsam Kang, Sooin Lim, Wookrae Kim, Jung Ryul Kim, Jai Hyung Lee, Kyungwon An

Research output: Contribution to journalArticlepeer-review

147 Citations (Scopus)


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 4π symmetry was demonstrated. Consequently, the cavity transmission at the quasieigenstate was observed to exhibit a critical behavior at the EP.

Original languageEnglish
Article number153601
JournalPhysical review letters
Issue number15
Publication statusPublished - 2010 Apr 13

ASJC Scopus subject areas

  • General Physics and Astronomy


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