Novel Entanglement-preserving approach for universal dissipation mechanisms in quantum nanophotonics

Ubiquitously in quantum nanophotonics, photons may be scattered off system impurities to the reservoir, or absorbed by reservoir degrees of freedom, which manifest as different dissipation mechanisms of scattering loss or material loss. Conventionally, fruitful density matrix approach (DMA) is adopted to study such effects, which averages out reservoir degrees of freedom in the reduced density matrix dynamics. While such an approach can incorporate the information that shuttles back and forth between system and reservoir, it does not preserve photon-photon entanglement in the system or the system-reservoir entanglement.

Here we present a novel wave-function-based approach that preserves the entanglement information, to study both dissipation mechanisms for an arbitrary photonic Fock state process. For the scattering loss scenario, when the dissipated photon does not return to the system, we show that the effects can be incorporated by using a reduced Hamiltonian description. For the material loss scenario, nonetheless, returning nature of dissipated photons fundamentally modifies multi-photon entanglement to invalidate the reduced Hamiltonian description. Moreover, our approach reveals how scattering matrix and transport properties are modified, which is beyond the scope of DMA.