title: Interaction-free measurements by quantum Zeno stabilization of ultracold atoms.
abstract: Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur. Interaction-free measurements (IFMs) exploit this counterintuitive influence to detect the presence of an object without requiring any interaction with it. Here we propose and realize an IFM concept based on an unstable many-particle system. In our experiments, we employ an ultracold gas in an unstable spin configuration, which can undergo a rapid decay. The object-realized by a laser beam-prevents this decay because of the indirect quantum Zeno effect and thus, its presence can be detected without interacting with a single atom. Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence. We demonstrate confidence levels of 90%, well beyond previous optical experiments.
authors: Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.
authors: J
authors: J
authors: Peise
authors: Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.
authors: B
authors: B
authors: Lücke
authors: 1] QSTAR, Largo Enrico Fermi 2, 50125 Firenze, Italy [2] Istituto Nazionale di Ottica, INO-CNR, Largo Enrico Fermi 2, 50125 Firenze, Italy [3] LENS Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
authors: L
authors: L
authors: Pezzé
authors: Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstraβe 2, D-30167 Hannover, Germany.
authors: F
authors: F
authors: Deuretzbacher
authors: Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.
authors: W
authors: W
authors: Ertmer
authors: QUANTOP, Institut for Fysik og Astronomi, Aarhus Universitet, 8000 Århus C, Denmark.
authors: J
authors: J
authors: Arlt
authors: 1] QSTAR, Largo Enrico Fermi 2, 50125 Firenze, Italy [2] Istituto Nazionale di Ottica, INO-CNR, Largo Enrico Fermi 2, 50125 Firenze, Italy [3] LENS Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
authors: A
authors: A
authors: Smerzi
authors: Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstraβe 2, D-30167 Hannover, Germany.
authors: L
authors: L
authors: Santos
authors: Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.
authors: C
authors: C
authors: Klempt