# Nonclassicality in off-resonant Raman process

## TL;DR

This paper investigates how off-resonant conditions in the Raman process can be used to generate and enhance nonclassical states, with detailed quantum analysis showing the significance of frequency detuning.

## Contribution

It provides a comprehensive quantum treatment of off-resonant Raman processes, highlighting the role of detuning in generating nonclassical states and analyzing various quantum correlations.

## Key findings

- Larger detuning enhances nonclassicality in some cases.
- Single- and two-mode squeezing and antibunching are observed.
- Intermodal entanglement is demonstrated.

## Abstract

Raman process is used for generation of nonclassical states and subsequent applications due to its simplicity. In view of the experimental feasibility of the off-resonant Raman process at single photon level useful in long distance quantum communication and quantum memory, we perform here a detailed study of possibility of generation of nonclassical states under off-resonance conditions. Specifically, we have studied nonclassicality in the off-resonant Raman process with the help of a characteristic function written using more general solution than the conventional short-time solution under complete quantum treatment and established the significance of frequency detuning parameter in generation of nonclassical states. The obtained characteristic function remains Gaussian and reveals that larger values of frequency detuning parameters are favorable to induce nonclassicality in some cases. The single- and two-mode squeezing and antibunching as well as intermodal entanglement are reported in terms of experimentally accessible quantum noise fluctuations considering either phonon mode coherent or chaotic. Subsequently, the joint photon number and integrated intensity distributions are studied to analyze the performance of pair generation in Stokes-phonon and pump-phonon modes. The present study discusses the role of resonance conditions in generation of nonclassical states and establishes that experimentally controllable detuning parameter can be used to probe and enhance the generated nonclassicality.