Atomic Focusing by Quantum Fields: Entanglement Properties

TL;DR

This paper investigates how quantum fields influence atomic beam coherence and entanglement during focusing, providing a detailed analysis of the atom-field entanglement effects on atomic coherence and purity.

Contribution

It extends the quantum lens model to analyze atom-field entanglement and its impact on atomic coherence and purity during the focusing process.

Findings

Entanglement reduces atomic coherence and purity.

Beam quality factor varies with photon number.

Closed-form dynamics of the focusing process are derived.

Abstract

The coherent manipulation of the atomic matter waves is of great interest both in science and technology. In order to study how an atom optic device alters the coherence of an atomic beam, we consider the quantum lens proposed by Averbukh et al [1] to show the discrete nature of the electromagnetic field. We extend the analysis of this quantum lens to the study of another essentially quantum property present in the focusing process, i.e., the atom-field entanglement, and show how the initial atomic coherence and purity are affected by the entanglement. The dynamics of this process is obtained in closed form. We calculate the beam quality factor and the trace of the square of the reduced density matrix as a function of the average photon number in order to analyze the coherence and purity of the atomic beam during the focusing process.