Landau-Zener transition stabilized by the enhanced quantum Zeno effect   in the bosonic system
  We study the Landau-Zener transition with the quantum Zeno effect in an open dissipative system populated by a large number of bosons. Given the quantum Zeno effect is strong enough, both discrete and continuous quantum Zeno measurements are found to stabilize the Landau-Zener transition. Both the $\sigma^x$-type longitudinal relaxation and $\sigma^z$-type transverse relaxation in the bosonic system are analyzed as a model of continuous quantum Zeno measurements. While both of them improve the signal-to-noise ratio in terms of the ground state population, the $\sigma^x$-type relaxation can further boost measurement sensitivity and thus lead to a polynomial speedup with the number of bosons in the system. For a system that contains a large number of bosons such as in a Bose-Einstein condensate with more than $10^4$ bosons, this equates to several orders of magnitude speedup. 
Kai Wen, Tim Byrnes, and Yoshihisa Yamamoto
quant-ph