Enhancing atom-light interactions with “selective radiance”: the recipe to exponentially improve photon storage fidelities
Abstract: Spontaneous emission, in which photons are absorbed by atoms and then re-scattered into undesired channels, fundamentally limits how strongly atoms interact with preferred photonic modes. Typically, it is assumed that this re-scattering occurs independently, and at a rate given by a single isolated atom, which in turn gives rise to standard limits of fidelity in applications such as quantum memories for light or photonic quantum gates. We find that this assumption does not hold when atoms are close enough to each other so that they give rise to collective subradiant states, whose free-space decay is significantly suppressed. Inspired by subradiance, we introduce the new concept of "selective radiance". Whereas subradiant states experience a reduced coupling to all optical modes, selectively-radiant states are tailored to radiate efficiently into a desired channel and very inefficiently into undesired channels, thus enabling an enhanced atom-light interface. We show that these states naturally appear in chains of atoms coupled to nanophotonic structures, and analyze the performance of photon storage in this setting. We numerically find that selectively radiant states allow for a photon storage error that performs exponentially better with number of atoms than previously known bounds.