Coherent control of collective atom phase for ultralong, inversion-free photon echoes

TL;DR

This paper introduces a coherent control method for collective atoms to generate inversion-free photon echoes, enabling ultralong, noise-free quantum memories suitable for long-distance quantum communication.

Contribution

It presents a novel phase-controlled double rephasing scheme that eliminates population inversion and quantum noise in photon echoes, extending storage times.

Findings

Inversion-free photon echoes achieved without spontaneous emission noise

Extended quantum memory storage times demonstrated

Potential application in long-distance quantum communication

Abstract

To overcome fundamental limitations of the \pi optical pulse-induced population inversion and optical decay-caused short storage time in conventional photon echoes, a coherent control of collective atoms is studied for inversion-free, optical decay-halted photon echoes, where the constraint of photon storage time is now replaced by a spin population decay process. Using phase-controlled double rephasing, an inversion-free photon echo scheme is obtained, where no spontaneous or stimulated emission-driven quantum noise exists. Thus, the present method can be applied for ultralong quantum memories in quantum repeaters for long-distance quantum communications.