In a new paper in Physical Review Letters, IFIMAC researchers Anael Ben-Asher, Antonio I. Fernández Domínguez and Johannes Feist have identified a novel mechanism that enables the efficient emission of single photons, which is a crucial requirement for various applications in quantum information. This mechanism, termed as non-Hermitian photon blockade (NHPB), opens up a new path for the development of high-performance single-photon sources.
Unlike conventional mechanisms that rely on anharmonicity in energy levels, the NHPB is achieved by manipulating the losses within the system rather than its energetic structure such that the system’s doubly excited state (reached by absorbing two photons) is much lossier than the singly excited one. The doubly excited state in such a system possesses a broader energy-dependent density of states with a lower amplitude compared to the singly excited state due to the relation between the loss of the state and its linewidth. As a result, when the system absorbs a photon from an external driving laser, the NHPB prevents the absorption of a second photon. The system subsequently emits only that single photon, acting as an efficient single-photon source. The nonlinearity in losses that enables the NHPB is associated with anharmonicity in the imaginary parts of the eigenvalues of the effective non-Hermitian Hamiltonian describing the undriven system.
The NHPB mechanism offers several advantages over conventional methods for single-photon generation as it leverages potentially high loss rates without being limited by them. It can operate effectively in the weak-coupling regime of cavity quantum electrodynamical systems, making it more accessible and less demanding experimentally. The feasibility of the NHPB mechanism has been demonstrated theoretically in a realistic setup involving a hybrid metallodielectric cavity that is weakly coupled to a two-level emitter. In this setup, efficient single-photon emission has been showcased and quantified by the normalized zero-delay second-order correlation function. These findings pave the way for future experimental investigations and the potential implementation of the NHPB mechanism in practical quantum light sources. [Full article]
