Memory for Light as a Quantum Process

TL;DR

This paper presents a comprehensive quantum process tomography of an optical memory based on electromagnetically induced transparency, enabling precise prediction and verification of stored quantum states, including nonclassical states.

Contribution

It introduces a complete characterization method of an optical quantum memory using superoperator tomography under different conditions, advancing quantum storage analysis.

Findings

Successfully reconstructed the superoperator for the memory

Predicted the retrieval of various quantum states accurately

Verified nonclassicality for stored Gaussian states

Abstract

We report complete characterization of an optical memory based on electromagnetically induced transparency. We recover the superoperator associated with the memory, under two different working conditions, by means of a quantum process tomography technique that involves storage of coherent states and their characterization upon retrieval. In this way, we can predict the quantum state retrieved from the memory for any input, for example, the squeezed vacuum or the Fock state. We employ the acquired superoperator to verify the nonclassicality benchmark for the storage of a Gaussian distributed set of coherent states.