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arXiv:1206.1652 · Physical Review A

Macroscopic quantum coherence in spinor condensates confined in an anisotropic potential

Yixiao Huang, Yunbo Zhang, Rong Lü, Xiaoguang Wang, Su Yi

Published Oct 25, 2012• 20 citations
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Abstract

We investigate the macroscopic quantum spin coherence of a spinor condensate confined in an anisotropic potential. Under the single-mode approximation, we show that a spin-1 Rb condensate can be modeled as a biaxial quantum magnet. A direct consequence of the biaxial anisotropy is that the tunneling splitting oscillates as a function of the external magnetic field applied along the hard axis. We also propose an experimental scheme to detect the oscillatory behavior of the tunneling splitting by employing the Landau-Zener tunneling.

DOI
10.1103/physreva.86.043625

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We investigate the macroscopic quantum spin coherence of a spinor condensate confined in an anisotropic potential. Under the single-mode approximation, we show that a spin-1 Rb condensate can be modeled as a biaxial quantum magnet. A direct consequence of the biaxial anisotropy is that the tunneling splitting oscillates as a function of the external magnetic field applied along the hard axis. We also propose an experimental scheme to detect the oscillatory behavior of the tunneling splitting by employing the Landau-Zener tunneling.
We study the macroscopic quantum tunneling of magnetization of the F=1F=1F=1 spinor condensate interacting through dipole-dipole interaction with an external magnetic field applied along the longitudinal or transverse direction. We show that the ground state energy and the effective magnetic moment of the system exhibit an interesting macroscopic quantum oscillation phenomenon originating from the oscillating dependence of thermodynamic properties of the system on the vacuum angle. Tunneling between two degenerate minima are analyzed by means of an effective potential method and the periodic instanton method.
In a previous work [H. Pu, W. Zhang, and P. Meystre, Phys. Rev. Lett. 87, 140405 (2001)]], we have shown that a spinor condensate confined in a periodic or double-well potential exhibits ferromagnetic behavior due to the magnetic dipole-dipole interactions between different wells, and in the absence of external magnetic field, the ground state has a twofold degeneracy. In this work, we demonstrate the possibility of observing macroscopic quantum spin tunneling between these two degenerate states and show how the tunneling rate critically depends on the strength of the transverse field.
We study the spin distribution and macroscopic entanglement in spinor condensates confined in an anisotropic potential under external magnetic fields. Different types of magnetic phases can be reached by tuning the magnetic dipolar interaction strength by modifying the trapping geometry. We investigate the atom-number fluctuations of the ground state and show that the different internal hyperfine states exhibit super-Poissonian, Poissonian, and sub-Poissonian distributions with different trapping geometries and strengths of the external magnetic field. We also propose a scheme to create a macroscopic maximally entangled spin state by slowly sweeping the external magnetic field.
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