Fast manipulation of spin-wave excitations in an atomic ensemble

Abstract

We experimentally demonstrated a fast manipulation of two orthogonal spin-wave excitations in an ensemble of cold ${}^{87}$Rb atoms. The spin-wave manipulation is realized by transferring the excitations between two collective states, and a \ensuremath{\pi} rotation between the two spin waves is accomplished on a time scale of \ensuremath{\sim}100 ns. The multiple \ensuremath{\pi} rotations are completed based on the single \ensuremath{\pi} rotation. The results show that the retrieval optical signal from the manipulated spin waves gradually decreases along with the increasing of \ensuremath{\pi}-rotation numbers. The loss mechanism of spin waves caused by a Raman \ensuremath{\pi} rotation is simply analyzed, and the possible methods to mitigate the loss are discussed. Using multiple \ensuremath{\pi} rotations, one can implement the dynamical decoupling to protect the qubit memory in an atom ensemble from the influence of environmental noise.