Continuous variable versus EIT-based quantum memories

TL;DR

This paper compares various continuous-variable quantum memory schemes, including EIT, Faraday effect, and Raman coupling, analyzing their effectiveness in ideal light-atom state mapping with potential measurement and feedback enhancements.

Contribution

It provides a unified model for continuous-variable quantum memories and compares different schemes, highlighting conditions for ideal state transfer.

Findings

EIT-based schemes can achieve near-ideal mapping with proper preparation.

Measurement and feedback can enhance quantum memory performance.

Different interaction Hamiltonians offer various trade-offs in fidelity and complexity.

Abstract

We discuss a general model of a quantum memory for a single light mode in a collective mode of atomic oscillators. The model includes interaction Hamiltonians that are of second order in the canonical position and momentum operators of the light- and atomic oscillator modes. We also consider the possibility of measurement and feedback. We identify an interaction Hamiltonian that leads to an ideal mapping by pure unitary evolution and compare several schemes which realize this mapping using a common continuous-variable description. In particular we discuss schemes based on the off-resonant Faraday effect supplemented by measurement and feedback and proper preparation of the atoms in a squeezed state and schemes based on off-resonant Raman coupling as well as electromagnetically induced transparency (EIT).