We study dynamical tunneling in a near-integrable Hamiltonian with three
degrees of freedom. The model Hamiltonian does not have any discrete symmetry.
Despite this lack of symmetry we show that the mixing of near-degenerate
quantum states is due to dynamical tunneling mediated by the nonlinear
resonances in the classical phase space. Identifying the key resonances allows
us to suppress the dynamical tunneling via the addition of weak
counter-resonant terms.Comment: 4 pages, 4 figures (low resolution