# Hidden PT Symmetry and quantization of coupled-oscillators model of QASER

## TL;DR

This paper reveals a hidden PT symmetry in a coupled-oscillator model of QASER, explaining its gain mechanism through symmetry breaking and providing a quantum framework starting from quantum fluctuations.

## Contribution

It introduces a hidden PT symmetry in a simplified coupled-oscillator model of QASER and quantizes the system to understand quantum fluctuations.

## Key findings

- QASER gain arises from broken PT symmetry phase
- Hidden PT symmetry exists in the coupled-oscillator model
- Quantum Langevin equations describe the quantum starting point

## Abstract

Using Maxwell-Bloch equations it has been shown how the superradiance can lead to amplification and gain at a frequency much larger than the pumping frequency. This remarkable effect has been examined in terms of a simpler model involving two coupled oscillators with one of them paramet- rically driven. We show that this coupled oscillator model has a hidden parity-time (PT) symmetry for QASER, we thus bring PT symmetry to the realm of parametrically coupled resonators. More- over, we find that the QASER gain arises from the broken PT symmetry phase. We then quantize the simplified version of the QASER using quantum Langevin equations. The quantum description enables us to understand how the system starts from quantum fluctuations.