Selective creation of quasiparticles in trapped Bose condensates

We investigate theoretically the use of time-varying magnetic fields to selectively create and manipulate quasiparticles in magnetically trapped Bose condensates. To maximize the transition matrix element connecting two desired quasiparticle states, the spatial symmetry of the applied magnetic field must be tailored to exploit the different spatial distributions of magnetization in the two quasiparticle states. This “spatial magnetic resonance” effect is analogous to the Franck-Condon factor in electric dipole transitions in diatomic molecules. Experimentally, the spatial magnetic resonance technique may allow the creation of coherences between quasiparticle states, the inversion of quasiparticle state populations, the measurement of quasiparticle lifetimes ($T_1$) and decoherence times ($T_2$), the creation of quasiparticle echoes, etc., in analogy with conventional spin magnetic resonance.