# Emission of photon pairs by mechanical stimulation of the squeezed vacuum

## TL;DR

This paper proposes a feasible optomechanical method to observe the dynamical Casimir effect through mechanically-induced photon pair emission, avoiding the need for ultra-high mirror velocities or strong coupling.

## Contribution

It introduces a novel approach using detuned parametric driving to amplify the dynamical Casimir effect in an optomechanical system without extreme physical requirements.

## Key findings

- Demonstrates mechanically-induced two-photon hyper-Raman scattering.
- Shows that small squeezing can significantly amplify the DCE.
- Provides a practical implementation pathway for observing DCE.

## Abstract

To observe the dynamical Casimir effect (DCE) induced by a moving mirror is a long-standing challenge because the mirror velocity needs to approach the speed of light. Here, we present an experimentally feasible method for observing this mechanical DCE in an optomechanical system. It employs a detuned, parametric driving to squeeze a cavity mode, so that the mechanical mode, with a typical resonance frequency, can parametrically and resonantly couple to the squeezed cavity mode, thus leading to a resonantly amplified DCE in the squeezed frame. The DCE process can be interpreted as {\it mechanically-induced two-photon hyper-Raman scattering} in the laboratory frame. Specifically, {\it a photon pair} of the parametric driving absorbs a single phonon and then is scattered into an anti-Stokes sideband. We also find that the squeezing, which additionally induces and amplifies the DCE, can be extremely small. Our method requires neither an ultra-high mechanical-oscillation frequency (i.e., a mirror moving at nearly the speed of light) nor an ultrastrong single-photon optomechanical coupling and, thus, could be implemented in a wide range of physical systems.