Beyond the spin model approximation for Ramsey spectroscopy
A Koller, M Beverland, Alexey Gorshkov, Ana Maria Rey
Ramsey spectroscopy has become a powerful technique for probing non-equilibrium dynamics of internal (pseudospin) degrees of freedom of interacting systems. In many theoretical treatments, the key to understanding the dynamics has been to assume the external (motional) degrees of freedom are decoupled from the pseudospin degrees of freedom. Determining the validity of this approximation also known as the spin model approximation is complicated, and has not been addressed in detail. Here we shed light in this direction by calculating Ramsey dynamics exactly for two interacting spin-1/2 particles in a harmonic trap. We focus on s-wave-interacting fermions in one and two-dimensional geometries. We nd that in 1D the spin model assumption works well over a wide range of experimentally-relevant conditions, but can fail at time scales longer than those set by the mean interaction energy. Surprisingly, in 2D a modi ed version of the spin model is exact to rst order in the interaction strength. This analysis is important for a correct interpretation of Ramsey spectroscopy and has broad applications ranging from precision measurements to quantum information and to fundamental probes of many-body systems.
, Beverland, M.
, Gorshkov, A.
and Rey, A.
Beyond the spin model approximation for Ramsey spectroscopy, Physical Review Letters, [online], https://doi.org/10.1103/PhysRevLett.112.123001, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915063
(Accessed September 27, 2023)