By: Dmitry Zezyulin
At: Instituto de Investigação Interdisciplinar, Anfiteatro
Quantum Zeno effect is a fundamental result in the quantum measurement theory. This effect consists in slowing down the dynamics of a quantum system subjected to frequent measurements or to a strong coupling to another quantum system. The Zeno effect can also be understood in more general terms as the changing a decay law of a quantum system depending on the frequency of measurements. If we apply this definition to a macroscopic quantum system, like a gas of condensed bosonic atoms, and take into account that in the macroscopic dynamics the frequency of measurements can be interpreted as the strength of the induced dissipation, then the effect of the measurement on the decay of the system can be viewed as the effect of dissipation on the macroscopic characteristics of the system. In order to emphasize the distinction of the latter statement of the problem with respect to already standard and widely accepted notion of quantum Zeno effect, we refer to the macroscopic Zeno effect bearing in mind its mean-field manifestation.
We theoretically demonstrate the possibility to observe the macroscopic Zeno effect for nonlinear waveguides with a localized dissipation. We study one- and two-dimensional waveguides governed by the nonlinear SchrÃ¶dinger equation and show the existence of stable stationary flows, which are balanced by the losses in the dissipative domain in the center of the waveguide. The macroscopic Zeno effect manifests itself in the non-monotonic dependence of the stationary flow on the strength of the dissipation. In particular, we highlight the importance of the parameters of the dissipation to observe the phenomenon. Our results are applicable to a large variety of systems, including condensates of atoms or quasi-particles and optical waveguides.
Part of the talk is based on Ref. . I will also touch upon very recent experimental achievements related to this topic .
 D. A. Zezyulin, V. V. Konotop, G. Barontini, and H. Ott, Macroscopic Zeno effect and stationary flows in nonlinear waveguides with localized dissipation, Phys. Rev. Lett. 109, 020405 (2012).
 G. Barontini, R. Labouvie, F. Stubenrauch, A. Vogler, V. Guarrera, and H. Ott, Controlling the dynamics of an open many-body quantum system with localized dissipation, Phys. Rev. Lett. 110, 035302 (2013).