Hidden PT symmetry and quantization of a coupled-oscillator model of quantum amplification by superradiant emission of radiation
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2017 American Physical Society. With Maxwell-Bloch equations how the superradiance can lead to amplification and gain at a frequency much larger than the pumping frequency has been shown. This remarkable effect has been examined in terms of a simpler model involving two coupled oscillators, with one of them parametrically driven. We show that this coupled-oscillator model has a hidden parity-time (PT) symmetry for quantum amplification by superradiant emission of radiation (QASER); we thus bring PT symmetry to the realm of parametrically coupled resonators. Moreover, we find that the QASER gain arises from the broken-PT-symmetry phase. We then quantize the simplified version of QASER using quantum Langevin equations. The quantum description enables us to understand how the system starts from quantum fluctuations.