Fractional photon-assisted tunneling for Bose-Einstein condensates in a double well

Half-integer-photon resonances in a periodically shaken double well are investigated on the level of the N-particle quantum dynamics. Contrary to nonlinear mean-field equations, the linear N-particle Schroumldinger equation does not contain any nonlinearity which could be the origin of such resonances. Nevertheless, analytic calculations on the N-particle level explain why such resonances can be observed even for particle numbers as low as N=2. These calculations also demonstrate why fractional photon resonances are not restricted to half-integer values.