A gas-filled fiber seems to be a strange contender for the gateway to the quantum world, but its simplicity hides a great power. When shone upon by laser light, this device enables cool and practical phenomena that are very useful for quantum experiments. For example, an intense light entering the tube can be mixed with other photons, the particles of light, to generate a new stream of photons with the desired properties, or even a pair of entangled photons.