Coherent competition and control between three-wave mixing and four-wave mixing in superconducting circuits

Exploring intermixing and interplay between different frequency-mixing processes has always been one of the interesting subjects at the interface of nonlinear optics with quantum optics. Here we investigate coherent competition and control between three-wave mixing (TWM) and four-wave mixing (FWM) in a cyclic three-level superconducting quantum system. In the weak control-field regime, strong competition leads to an alternating oscillation between TWM and FWM signals and this oscillation is a signature of strong energy exchange between these two nonlinear processes. In particular, such oscillation is absent from conventional multi-wave mixing in atomic systems. Surprisingly, synchronous TWM and FWM processes are demonstrated in the strong control-field regime and, at the same time, their efficiencies can be as high as 40% and 45%, respectively. Our study shows that these competitive behaviors between TWM and FWM can be manipulated by tuning the control-field intensity

GRB 221009A: revealing a hidden afterglow during the prompt emission phase with Fermi-GBM observations

Recently, LHAASO reported the detection of brightest-of-all-time GRB 221009A, revealing the early onset of a TeV afterglow. However, there is no evidence of afterglow emission at such early time at other wavelengths. Here we report the discovery of a hidden afterglow component during the prompt emission phase with Fermi Gamma-Ray Burst Monitor (GBM) observations. We analyze the spectral evolution of the X-ray/$\gamma$-ray emission of GRB 221009A measured by GBM during the dips of two prompt emission pulses (i.e., intervals $T_{0}+[300-328]\rm~s$ and $T_{0}+[338-378]\rm~s$, where $T_0$ is the GBM trigger time). We find that the spectra at the dips transit from the Band function to a power-law function, indicating a transition from the prompt emission to the afterglow. After $\sim T_{0}+ 660 \rm~s$, the spectrum is well described by a power-law function and the afterglow becomes dominant. Remarkably, the underlying afterglow emission at the dips smoothly connect with the afterglow after $\sim T_{0}+ 660 \rm~s$. The entire afterglow emission measured by GBM can be fitted by a power-law function $F\sim t^{-0.95\pm0.05}$, where $t$ is the time since the first main pulse at $T^*=T_0+226~{\rm s}$, consistent with the TeV afterglow decay measured by LHAASO. The start time of this power-law decay indicates that the afterglow peak of GRB 221009A should be earlier than $T_{0}+300 \rm ~s$. We also test the possible presence of a jet break in the early afterglow light curve, finding that both the jet break model and single power-law decay model are consistent with the GBM data. The two models can not be distinguished with the GBM data alone because the inferred jet break time is quite close to the end of GBM observations.Comment: 8 pages, 4 figures and 2 table