Abstract
Coupling photons to Rydberg excitations in a cold atomic gas yields unprecedentedly large optical nonlinearities at the level of individual light quanta, where the formation of nearby dark-state polaritons is blocked by the strong interactions between Rydberg atoms. This blockade mechanism, however, realizes an inherently dissipative nonlinearity, which limits the performance of practical applications. In this work, we propose a new approach to strong photon interactions via a largely coherent mechanism at drastically suppressed photon losses. Rather than a polariton blockade, it is based on an interaction induced conversion between distinct types of dark-state polaritons with different propagation characteristics. We outline a specific implementation of this approach and show that it permits to turn a single photon into an effective mirror with a robust and continuously tuneable reflection phase. We describe potential applications, including a detailed discussion of achievable operational fidelities.
Highlights
The notion that photons are devoid of mutual interactions in vacuum is well rooted in our elementary understanding of light
electromagnetically induced transparency (EIT) in these systems is based on the formation of Rydberg dark-state polaritons, which correspond to coherent superposition states of light and matter that are immune to dissipation [46,47]
We devise a new approach to engineering effective photon interactions via particle interactions in an EIT medium
Summary
The notion that photons are devoid of mutual interactions in vacuum is well rooted in our elementary understanding of light. EIT in these systems is based on the formation of Rydberg dark-state polaritons, which correspond to coherent superposition states of light and matter that are immune to dissipation [46,47] While this polariton formation supports the lossless and form-stable propagation of single photons, the strong mutual interaction between two such polaritons. The devised strategy can be understood as a dark-state polariton switch, as opposed to the existing schemes based on the polariton blockade, Fig. 1(a) This new mechanism globally preserves EIT conditions such that nonlinear dissipation is intrinsically suppressed, thereby alleviating the decoherence-related hindrances discussed in Refs. We discuss the performance of such applications based on current technology and in relation to previous blockade-based approaches
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