Quantum Memory for Photons in Case of Many Close Lying Exciton Resonances in Solids

TL;DR

This paper investigates quantum memory for photons in solids with multiple close-lying exciton resonances, demonstrating conditions under which quantum pulses can be stored and reconstructed with minimal distortion.

Contribution

It introduces a model for photon storage using resonant exciton states with Fano resonances, analyzing the effects of various parameters on pulse preservation.

Findings

Quantum pulse slowing to below vacuum speed is feasible.

Storage fidelity depends on Fano parameters, detuning, and decoherence.

Pulse shape and quantum state can be restored under specific conditions.

Abstract

The possibility of storage of quantum information with photons is studied in the case of resonant transitions via many close lying exciton levels in a solid with impurity Lambda-atoms. The upper levels of the impurity atom form resonant Fano states, similar to the autoionization atomic states, due to the configuration interaction with the continuum of the exciton band. In this case slowing of light pulses is shown to be realistic, in the presence of the control field, down to the group velocity much lower than that in vacuum. The possibility of storage and reconstruction of a quantum pulse is studied in the case of the instantaneous switching on/off of the control field. It is shown that the signal quantum pulse cannot be stored undistorted for differing values of Fano parameters and for non-zero two-photon detuning and decay rate between the lower levels (decoherence). However, for small difference of the Fano parameters and for small values of the two-photon detuning and the decoherence there is no distortion in the case where the length of the pulse is much longer than the linear absorption (amplification) length, so the shape and quantum state of the light pulse can be restored.