Polariton-polariton interaction constants in microcavities. Dark solitons in high velocity waveguide polariton fluids. Polariton laser using single micropillar GaAs-GaAlAs semiconductor cavities. Observation of optical-fibre kerr nonlinearity at the single-photon level. Matsuda, N., Shimizu, R., Mitsumori, Y., Kosaka, H. A single-photon switch and transistor enabled by a solid-state quantum memory. A photon–photon quantum gate based on a single atom in an optical resonator. Ultrafast photon-photon interaction in a strongly coupled quantum dot-cavity system. Controlled phase shifts with a single quantum dot. Nonlinear π phase shift for single fibre-guided photons interacting with a single resonator-enhanced atom. Conditional π-phase shift of single-photon-level pulses at room temperature. Sagona-Stophel, S., Shahrokhshahi, R., Jordaan, B., Namazi, M. Optical π phase shift created with a single-photon pulse. Large cross-phase modulations at the few-photon level. Low-power cross-phase modulation in a metastable xenon-filled cavity for quantum-information applications. Phase modulation at the few-photon level for weak-nonlinearity-based quantum computing. Measurement of conditional phase shifts for quantum logic. Single-photon Kerr nonlinearities do not help quantum computation. Exciton-polaritons in lattices: a non-linear photonic simulator. Emergence of quantum correlations from interacting fibre-cavity polaritons. Towards polariton blockade of confined exciton–polaritons. Two photons co- and counterpropagating through N cross-Kerr sites. Nonlinear quantum optical computing via measurement. Entangled-coherent-state quantum key distribution with entanglement witnessing. Quantum metrology with entangled coherent states. High-efficiency quantum-nondemolition single-photon-number-resolving detector. Complete quantum teleportation with a kerr nonlinearity. With our work serving as a stepping stone, we lay down a route for quantum information processing in polaritonic lattices. We observe cross-phase modulation of up to 3 ± 1 mrad per polariton using laser beams attenuated to below the average intensity of a single photon. These combine the strong interactions of excitons 9, 10 with the scalability of micrometre-sized emitters 11. In this work we show that the required nonlinearity can be provided by exciton–polaritons in micropillars with embedded quantum wells. This approach underpins many proposed applications in quantum optics 1, 2, 3, 4, 5, 6, 7 and information processing 8, but achieving its potential requires strong single-photon-level nonlinear phase shifts as well as scalable nonlinear elements. The second key ingredient for quantum photonics is interactions between photons, which can be provided by optical nonlinearities in the form of cross-phase modulation. Photonic platforms are an excellent setting for quantum technologies as weak photon–environment coupling ensures long coherence times.

Cross phase coherence