Non-Hermitian Electromagnetically Induced Transparency

Electromagnetically induced transparency (EIT) and amplification (EIA) are widely applied in slowing light, frequency filtering, sensing, and transduction. While EIT/A are typically implemented with Hermitian (coherent) coupling, in this work, we study the possible EIT/A effects when the coupling is non-Hermitian. We find that the scattering relation of Hermitian EIT is identical to that of anti-Hermitian (purely dissipative) EIA, and identify its origin as the symmetry of Hamiltonian under particle-hole transformation. We also conduct a self-consistent quantum analysis to understand the fundamental noise in EIT/A. Surprisingly, pure dissipation can implement the standard EIT effect with arbitrarily suppressed noise. Furthermore, we reveal that the added noise in standard EIA is not quantum limited. By incorporating both coherent and dissipative couplings, we identify a new regime of anomalous EIA, where the added noise is suppressed and the gain-bandwidth tradeoff is surpassed.  Our results offer new possibilities in controlling quantum light.