Experimental observation of coherent-perfect-absorber and laser points in anti-PT symmetry

The coexistence of coherent perfect absorber and laser or amplifier (CPAL) point is a peculiar spectral singularity associated with the scattering matrices of non-Hermitian systems. While the potential of CPAL systems for sensing application has been highlighted recently, the extreme sensitivity of parity-time ($\mathrm{P}\mathrm{T}$)-symmetric CPAL devices to the input signal deviations has so far impeded their practical utilization. Here we explore a strategy for implementing CPAL circuits by exploiting another type of non-Hermitian symmetry, namely anti-$\mathrm{P}\mathrm{T}$ ($\text{A}\mathrm{P}\mathrm{T}$) symmetry. We demonstrate that the condition for building CPAL in our proposed $\text{A}\mathrm{P}\mathrm{T}$-symmetric electronic circuits additionally requires parity symmetry, which simplifies the circuit design and implementation. Additionally, we show that this newly proposed structure is 1.85 times more robust compared to previous CPAL devices studied in the literature.