Abstract
Achieving strong interactions between individual photons enables a wide variety of exciting possibilities in quantum information science and many-body physics. Cold atoms interfaced with nanophotonic structures have emerged as a platform to realize novel forms of nonlinear interactions. In particular, when atoms are coupled to a photonic crystal waveguide, long-range atomic interactions can arise that are mediated by localized atom-photon bound states. We theoretically show that in such a system, the absorption of a single photon can change the band structure for a subsequent photon. This occurs because the first photon affects the atoms in the chain in an alternating fashion, thus leading to an effective period doubling of the system and a new optical band structure for the composite atom-nanophotonic system. We demonstrate how this mechanism can be engineered to realize a single-photon switch, where the first incoming photon switches the system from being highly transmissive to highly reflective, and analyze how signatures can be observed via non-classical correlations of the outgoing photon field.
Highlights
Creating strong, controllable interactions between individual photons enables many opportunities [1] ranging from quantum information processing to the creation of strongly correlated quantum states of light [2, 3, 4, 5, 6]
A promising new approach is the field of waveguide QED [13, 14], made possible by experiments to interface atoms with propagating modes of nanophotonic systems including nanofibers [15] and photonic crystal waveguides (PCWs) [16, 17, 18, 19]
We exploit that for an atomic lattice trapped with the PCW periodicity, atom-atom interactions naturally alternate in sign due to the Bloch structure of the underlying optical modes
Summary
Controllable interactions between individual photons enables many opportunities [1] ranging from quantum information processing to the creation of strongly correlated quantum states of light [2, 3, 4, 5, 6]. The presence of one atomic excitation effectively creates a doubling of the atomic periodicity from the standpoint of a second propagating photon, resulting in a dramatic change of its dispersion relation. This should be contrasted with the qualitatively very different physics that arises for the case of spatially smooth atomic interactions, which has been separately analyzed before for PCWs [26, 27] and lies at the heart of optical nonlinearities involving Rydberg gases [10, 11, 12].
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