Quantum Acoustic Phonon Sound Laser as Virtual Phonons creating light?

 A sound laser is characterized by the stimulated coherent emission of acoustic phonons and is also commonly referred to as a “phonon laser”.^{4,100,117,118} The phonon lasing action has been theoretically advised and experimentally reported in several optomechanical systems at different acoustic frequencies ranging from MHz to hundreds of GHz.^{4,100,118–122} At ultrahigh frequencies, the experimental observation of phonon amplification has been reported in hybrid systems coupling Bose-Einstein condensates with acoustic phonons⁴ and in semiconductor superlattices exploiting electron–phonon interactions.¹⁰⁰

https://pubs.aip.org/aip/apl/article/122/14/140501/2882348 

  A significant case is the creation of quantum light sources in which coupling between single photons and phonons can be controlled and harnessed to enable quantum information transduction.

Tarrago Velez, Santiago, Vivishek Sudhir, Nicolas Sangouard, and Christophe Galland. “Bell correlations between light and vibration at ambient conditions.” Science Advances 6, no. 51 (2020): eabb0260.

 spontaneously created between light and vibration during the Raman interaction. Here, we present a scheme leveraging universal properties of spontaneous Raman scattering to demonstrate Bell correlations between light and a collective molecular vibration. We measure the decay of these hybrid photon-phonon Bell correlations with sub-picosecond time resolution and find that they survive over several hundred oscillations at ambient conditions.

Creating and detecting quantum entanglement between light and atomic vibrations at room temperature - video

 ultrasound laser frequency so the air is a nonlinear medium - vid

Quicycle papers

 https://quicycle.com/quicyclejournal/#QJ0017

 Paul S. Wesson pdf

 Photon creation can still occur through transitions from positive to negative frequencies. In the quantum case this implies that a synthetically moving structure would spontaneously emit radiation even when impedance matched. The significance of impedance matching relates to black hole radiation where in the vicinity of the Schwarzschild singularity the effective values of permittivity and permeability are impedance matched and therefore according to our theorems radiation can only occur if negative frequencies are included.

Photon conservation in trans-luminal metamaterials 

negative frequencies must be interpreted as
positive energies. This we address by inverting the sign of both the frequency and the wave
vector thus retaining the reality of a wave headed in the same direction as before the inversion