Physical Review A
Berry phase in controlled light propagation and storage
Andrzej Raczyński, Jarosław Zaremba, Sylwia Zielińska‐Raczyńska
Abstract
It is shown that during light storage in an atomic medium in the $\mathrm{\ensuremath{\Lambda}}$ configuration, with not only the amplitude of the control field but also its phase changing adiabatically, a photon gains a Berry (geometric) phase. In the case of the tripod configuration with two probe fields the Berry phase is replaced by a $2\ifmmode\times\else\texttimes\fi{}2$ matrix. The probe fields are shown to be superpositions of two modes, each of them being characterized not only by its own velocity but also by its own Berry phase. If after light storage photons are released backwards, the contributions of the two modes interfere and the distribution of the outgoing photons can be steered by changing the difference between the Berry phases of the modes, due to the choice of the control field at the storage and release stages. In particular, one can turn a single photon of one of the probe fields into a photon of the other field or essentially modify coherent states of the incoming pulses.