23 research outputs found
Emergence and destruction of macroscopic wave functions
The concept of the macroscopic wave function is a key for understanding
macroscopic quantum phenomena. The existence of this object reflects a certain
order, as is present in a Bose-Einstein condensate when a single-particle
orbital is occupied by a macroscopic number of bosons. We extend these ideas to
situations in which a condensate is acted on by an explicitly time-dependent
force. While one might assume that such a force would necessarily degrade any
pre-existing order, we demonstrate that macroscopic wave functions can persist
even under strong forcing. Our definition of the time-dependent order parameter
is based on a comparison of the evolution of -particle states on the one
hand, and of states with particles on the other. Our simulations
predict the possibility of an almost instantaneous dynamical destruction of a
macroscopic wave function under currently accessible experimental conditions.Comment: 6 pages, 5 figure
Spatial two-particle NOON-states in periodically shaken three-well potentials
Few-particle dynamics in a three-well potential are investigated numerically. It is shown that periodically shaking the potential can considerably increase the fidelity of emerging spatial quantum superpositions. Such NOON-states are important for quantum interferometry. If the two particles initially sit in the middle well, the probability to return to this state can distinguish pure quantum dynamics from statistical mixtures. The numeric implementation of decoherence via particle losses shows clear differences from the pure quantum behaviour. A three-well lattice could be an ideal system for experimental realizations
Entangling two distinguishable quantum bright solitons via collisions
The generation of mesoscopic Bell states via collisions of distinguishable bright solitons has been suggested in Phys. Rev. Lett. 111, 100406 (2013). Here, we extend our former proposal to two hyperfine states of 85Rb instead of two different atomic species, thus simplifying possible experimental realisations. A calculation of the s-wave scattering lengths for the hyperfine states (f,mf) = (2, +2) and (3, +2) identifies parameter regimes suitable for the creation of Bell states with an advantageously broad Feshbach resonance. We show the generation of Bell states using the truncated Wigner method for the soliton's centre of mass and demonstrate the validity of this approach by a comparison to a mathematically rigorous effective potential treatment of the quantum many-particle problem