24 research outputs found
Quantum reactive scattering in the long-range ion-dipole potential
An ion and a polar molecule interact by an anisotropic ion-dipole potential
scaling as at large distances. Due to its
long-range character, it modifies the properties of angular wave functions,
which are no longer given by spherical harmonics. In addition, an effective
centrifugal potential in the radial equation can become attractive for low
angular momenta. In this paper, we develop a general framework for an
ion-dipole reactive scattering, focusing on the regime of large . We
introduce modified spherical harmonics as solutions of the angular part of the
Schr\"odinger equation and derive several useful approximations in the limit of
large . We present a formula for the scattering amplitude expressed in
terms of the modified spherical harmonics and we derive expressions for the
elastic and reactive collision rates. The solutions of the radial equation are
given by Bessel functions, and we analyse their behaviour in two distinct
regimes corresponding, basically, to attractive and repulsive long-range
centrifugal potentials. Finally, we study reactive collisions in the universal
regime, where the short-range probability of loss or reaction is equal to
unity.Comment: 19 pages, 11 figures, 5 appendice
Multipartite-Entanglement Dynamics in Regular-to-Ergodic Transition: a Quantum-Fisher-Information approach
The characterization of entanglement is a central problem for the study of
quantum many-body dynamics. Here, we propose the quantum Fisher information as
a useful tool for the study of multipartite-entanglement dynamics in many-body
systems. We illustrate this by considering the regular-to-ergodic transition in
the Dicke model---a fully-connected spin model showing quantum thermalization
above a critical interaction strength. We show that the QFI has a rich
dynamical behavior which drastically changes across the transition. In
particular, the asymptotic value of the QFI, as well as its characteristic
timescales, witness the transition both through their dependence on the
interaction strength and through the scaling with the system size. Since the
QFI also sets the ultimate bound for the precision of parameter estimation, it
provides a metrological perspective on the characterization of entanglement
dynamics in many-body systems. Here we show that quantum ergodic dynamics
allows for a much faster production of metrologically useful states.Comment: 9 pages, 10 figure
Generation of scalable many-body Bell correlations in spin chains with short-range two-body interactions
Dynamical generation of strong and scalable quantum resources, like many-body
entanglement and Bell correlations, in spin- chains, is possible with
all-to-all interactions, either for constant interaction strength realizing
one-axis twisting protocol or for power-law decaying potentials. We show,
however, that such quantum resources can also be dynamically generated with a
finite range of interactions. We identify a necessary critical range and
indicate a critical time when scalable quantum correlations appear. Finally, we
show that the certification of generated states is accessible in the modern
quantum simulator platforms.Comment: 6 figure