# Intrinsic cross-Kerr nonlinearity in an optical cavity containing an interacting Bose-Einstein condensate

## TL;DR

This paper investigates the intrinsic cross-Kerr nonlinearity in an optical cavity with a Bose-Einstein condensate, revealing its effects on bistability, quantum fluctuations, and quadrature squeezing, especially under strong driving conditions.

## Contribution

It demonstrates the presence and influence of intrinsic cross-Kerr nonlinearity in a BEC-cavity system, including its competition with atom-atom interactions and its role in quantum squeezing.

## Key findings

- CK nonlinearity affects bistability at high laser intensities
- Atom-atom interactions can neutralize CK effects
- Enhanced s-wave scattering leads to strong quadrature squeezing

## Abstract

An interacting cigar-shaped Bose-Einstein condensate (BEC) inside a driven optical cavity exhibits an intrinsic cross-Kerr (CK) nonlinearity due to the interaction with the optical mode of the cavity. Although the CK coupling is much weaker than those of the radiation pressure and the atom-atom interactions, it can affect the bistability behavior of the system when the intensity of the laser pump is strong enough. On the other hand, there is a competition between the CK nonlinearity and the atom-atom interaction so that the latter can neutralize the effect of the former. Furthermore, the CK nonlinearity causes the effective frequency of the Bogoliubov mode of the BEC as well as the quantum fluctuations of the system to be increased by increasing the cavity driving rate. However, in the dispersive interaction regime the effect of the CK nonlinearity is negligible. In addition, we show that by increasing the \textit{s}-wave scattering frequency of atomic collisions one can generate a strong stationary quadrature squeezing in the Bogoliubov mode of the BEC.