Researchers at the Max Planck Institute for the Science of Light and Jozef Stefan Institute have successfully demonstrated spontaneous parametric down-conversion (SPDC) in a liquid crystal for the first time. This breakthrough, published in Nature, paves the way for a new generation of quantum sources that are efficient and tunable with an electric field. SPDC involves splitting a single photon into two, creating entangled photon pairs and other complex states of light crucial for optical quantum technologies.
SPDC relies on breaking central symmetry, which is only possible in crystals with a centrally asymmetric elementary cell. Ordinary liquids and gases, being isotropic, do not allow for SPDC to occur. However, researchers have identified ferroelectric nematic liquid crystals with a unique structure that exhibit strong central symmetry breaking. These materials have elongated, asymmetric molecules that can be re-oriented by an external electric field, enabling the production of photon pairs with adjustable polarization properties and generation rates.
The samples used in the experiment were prepared by the Jozef Stefan Institute from a ferroelectric nematic liquid crystal synthesized by Merck Electronics KGaA. By implementing SPDC in a liquid crystal, researchers achieved similar efficiency in entangled photon generation as the best nonlinear crystals, such as lithium niobate, of similar thickness. Additionally, by applying a small electric field, they could control the generation of photon pairs, turn it on and off, and modify the polarization properties. This groundbreaking discovery marks the beginning of a new era of quantum light sources that are flexible, tunable, and highly efficient.
The ability to tune the properties of photon pairs using an electric field represents a significant advancement in quantum technology. This innovation allows for the creation of more complex devices that can be integrated into various applications. The new generation of quantum light sources offers versatility and efficiency that traditional sources cannot match, opening up a host of possibilities for quantum physics and technology. The liquid crystal platform provides a promising avenue for further research and development in the field of quantum photonics.
The successful implementation of SPDC in a liquid crystal marks a significant milestone in the field of quantum physics and quantum technology. The unique properties of ferroelectric nematic liquid crystals make them ideal candidates for efficient production of entangled photon pairs and other quantum states of light. By leveraging the central symmetry breaking capability of these materials, researchers have unlocked a new level of control and flexibility in generating quantum light. This achievement sets the stage for further advancements in quantum photonics and opens up new avenues for exploring the potential of quantum technologies.
Overall, the demonstration of SPDC in a liquid crystal represents a major breakthrough in the field of quantum optics. The ability to generate entangled photon pairs and manipulate their properties using an electric field in a liquid crystal platform offers new opportunities for advancing quantum technologies. The findings of this study published in Nature have significant implications for the development of efficient, tunable, and flexible quantum light sources. This research not only expands our understanding of quantum physics but also holds promise for practical applications in quantum communication, sensing, and computing.