Abstract
We theoretically 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.
Highlights
Quantum control of atom–photon interactions is a prerequisite for the realization of quantum networks based on single photons as flying qubits [1, 2]
Schemes based on heralded state transfer have been realized [10, 12,13,14], and fiber-coupled resonators coupled to single atoms have been used to perform SWAP gates [15, 16]
Storage efficiencies of the order of 22% have been reported for a quantum memory composed by a single atom in an optical cavity [17]
Summary
Luigi Giannelli , Tom Schmit, Tommaso Calarco, Christiane P Koch , Stephan Ritter and Giovanna Morigi.
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