Understanding of collective atom phase control in modified photon echoes for a near perfect, storage time extended quantum memory

TL;DR

This paper analyzes a photon echo-based quantum memory protocol using Maxwell-Bloch equations in a three-level system, demonstrating classical control over quantum states and phase matching for improved storage times.

Contribution

It introduces a method to control quantum coherence and propagation direction in a three-level photon echo system using phase matching and Rabi flopping, extending quantum memory capabilities.

Findings

Backward photon echo scheme with coherence conversion enhances storage time.

Control pulses can manipulate phase and direction of photon echoes.

Limitations identified in phase change with arbitrary control pulse areas.

Abstract

A near perfect, storage time-extended photon echo-based quantum memory protocol has been analyzed by solving the Maxwell-Bloch equations for a backward scheme in a three-level system. The backward photon echo scheme is combined with a controlled coherence conversion process via control Rabi flopping to a third state, where the control Rabi flopping collectively shifts the phase of the ensemble coherence. The propagation direction of photon echoes is coherently determined by the phase matching condition between the data (quantum) and the control (classical) pulses. Herein we discuss the classical controllability of a quantum state for both phase and propagation direction by manipulating the control pulses in both single and double rephasing photon echo schemes of a three-level system. Compared with their well-understood use for two-level photon echoes, the Maxwell-Bloch equations to a three-level system have a critical limitation regarding the phase change when interacted with an arbitrary control pulse area.