Enhancing Quantum Communication Devices with Liquid Crystals

The liquid crystals found in television screens have made it easy to produce quantum light.

Light, with its quantum properties, is important for many future technologies: such entangled particles in light could help build quantum communication networks that support an unhackable internet, as well as quantum imaging techniques for biomedical applications. Matyas Humar Despite these advanced applications, the method for generating quantum light has remained largely unchanged for 60 years, says a researcher at the Jozef Stefan Institute in Slovenia. He and his colleagues have devised a way to generate quantum light using liquid crystals.

Team Members Vitaly Sultanov Researchers at the Max Planck Institute in Germany say that traditionally, researchers shine a laser on special crystals to make them emit quantum light. In this technique, the structure of the crystal determines the properties of the light it emits, which in turn determines how it can be used. The only way to change these properties is to redo the experiment with new crystals, which is costly, time-consuming and impractical.

To get around this, the researchers used liquid crystals, a material made of rod-shaped molecules that can wobble like a liquid but adopt unusual arrangements like more conventional crystals. By exposing the liquid crystal to an electric field, they can tune its structure, and thus the properties of the quanta of light it emits when illuminated with a laser.

“In this respect, liquid crystals are the perfect material,” says Sultanov.

After several experiments, his team found that liquid crystals were much easier to tune than solid liquid crystals, and nearly as efficient at producing light filled with entangled particles.

“While the generated photons could conceivably have been produced using conventional crystals, the tunability of the entanglement could not,” he said. Miles Padgett “These advances are [quantum] “Imaging, Communication, Sensing”

Maria ChekhovaResearchers, also from the Max Planck Institute, say that using liquid crystals in quantum communication devices could make it easier to send information over multiple channels at once, because the liquid crystals can be tuned to produce quantum states of light that can encode large amounts of information in many of their properties.