Optimal storage of a single photon by a single intra-cavity atom

Abstract

Wetheoretically analyze the efficiency of a quantum memory for single photons. The photons
propagate along a transmission line and impinge on one of the mirrors of a high-finesse cavity. The
quantum memory is constituted by a single atom within the optical resonator. Photon storage is
realized by the controlled transfer of the photonic excitation into a metastable state of the atom and
occurs via a Raman transition with a suitably tailored laser pulse, which drives the atom. Our study is
supported by numerical simulations, in which we include the modes of the transmission line and we
use the experimental parameters of existing experimental setups. It reproduces the results derived
using input-output theory in the corresponding regimes and can be extended to compute dynamics
where the input-output formalism cannot be straightforwardly applied. Our analysis determines the
maximal storage efficiency, namely, the maximal probability to store the photon in a stable atomic
excitation, in the presence of spontaneous decay and cavity parasitic losses. It further delivers the form
of the laser pulse that achieves the maximal efficiency by partially compensating parasitic losses.We
numerically assess the conditions under which storage based on adiabatic dynamics is preferable to
non-adiabatic pulses. Moreover, we systematically determine the shortest photon pulse that can be
efficiently stored as a function of the system parameters.