Scattering by (entangled) spatial and spin degrees of freedom

E. Karlsson, Stephen William Lovesey

E. Karlsson, Stephen William Lovesey

Zhibing Li, Bao Cheng-guang, Wei Zheng

Abstract Condensate of spin-1 atoms frozen in a unique spatial mode may possess large internal degrees of freedom. The scattering amplitudes of polarized cold atoms scattered by the condensate are obtained with the method of fractional parentage coefficients that treats the spin degrees of freedom rigorously. Channels with scattering cross sections enhanced by the square of the atom number of the condensate are found. Entanglement between the condensate and the propagating atom can be established by scattering. Entanglement entropy is analytically obtained for arbitrary initial states. Our results also give a hint for the establishment of quantum thermal ensembles in the hyperfine space of spin states.

Lucas Lamata, Juan León

We consider the bipartite spin entanglement between two identical fermions generated in spin-independent scattering. We show how the spatial degrees of freedom act as ancillas for the creation of entanglement to a degree that depends on the scattering angle $\ensuremath{\theta}$. The number of Slater determinants generated in the process is greater than 1, corresponding to genuine quantum correlations between the identical fermions. The maximal entanglement attainable of 1 ebit is reached at $\ensuremath{\theta}=\ensuremath{\pi}∕2$. We also analyze a simple $\ensuremath{\theta}$-dependent Bell's inequality, which is violated for $\ensuremath{\pi}∕4<\ensuremath{\theta}\ensuremath{\leqslant}\ensuremath{\pi}∕2$. This phenomenon is unrelated to the symmetrization postulate but does not appear for unequal particles.

Elia Mantoan

E. Karlsson, Stephen William Lovesey

Allegations that our theoretical description of neutron scattering by entangled spin and spatial degrees of freedom is incorrect are shown to be misplaced for the allegations are derived from a naively incomplete, quantum mechanical calculation of neutron scattering by identical nuclei.