Quantum optics with quantum gases: Controlled state reduction by designed light scattering

Igor B. Mekhov, Helmut Ritsch

Research output

33 Citations (Scopus)


Cavity-enhanced light scattering from an ultracold gas in an optical lattice constitutes a quantum measurement with a controllable form of the measurement backaction. Time-resolved counting of scattered photons alters the state of the atoms without particle loss implementing a quantum nondemolition measurement. The conditional dynamics is given by the interplay between photodetection events (quantum jumps) and no-count processes. The class of emerging atomic many-body states can be chosen via the optical geometry and light frequencies. Light detection along the angle of a diffraction maximum (Bragg angle) creates an atom-number-squeezed state, while light detection at diffraction minima leads to the macroscopic superposition states (Schrödinger cat states) of different atom numbers in the cavity mode. A measurement of the cavity transmission intensity can lead to atom-number-squeezed or macroscopic superposition states depending on its outcome. We analyze the robustness of the superposition with respect to missed counts and find that a transmission measurement yields more robust and controllable superposition states than the ones obtained by scattering at a diffraction minimum.

Original languageEnglish
Article number013604
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number1
Publication statusPublished - 6 Aug 2009

Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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