To tackle the challenge of quantum information loss over long distances, one approach is to divide the network into smaller segments and connect them all using shared quantum states. This requires that quantum storage devices can "talk" to another device that allows for the creation of quantum information. Researchers from Germany and England have achieved this for the first time by creating a system that connects these two crucial components and uses conventional optical fiber to transmit quantum data. The findings have been published in the latest issue of Science Advances.
Dr. Sarah Thomas works in the Quantum Optics Lab. Image Source: Thomas Angus/Imperial College London
In conventional telecom systems, information may be lost during long-distance transmission. To address this, systems employ "repeaters" at fixed points to read and reamplify information, ensuring it reaches its destination intact.
However, classical repeaters cannot be used with quantum information because any attempt to read and copy it would destroy the information. This is somewhat advantageous because any attempt to "eavesdrop" on a quantum connection would disrupt the information and alert the users.
A way to maintain this advantage while overcoming the issue is by sharing quantum information in the form of entangled photons. Long-distance sharing of entanglement in quantum networks requires two types of devices: one for creating entangled photons and another for storing and allowing retrieval later.
The research team developed a system where two devices operate at the same wavelength. "Quantum dots" generate photons, which are then passed to the quantum storage system and stored in a cloud of rubidium atoms. Lasers can "open" and "close" the memory, thus storing and releasing photons as needed.
Not only do the wavelengths of these two devices match, but they are also the same as those used in today's telecom networks, allowing transmission through conventional optical fiber cables familiar in everyday internet use.
Dr. Sarah Thomas from the Department of Physics at Imperial College London notes that connecting these two key devices is a crucial step towards realizing a quantum network. Lucas Wagner from the University of Stuttgart in Germany adds that enabling connections between distant locations or even quantum computers is a key task for future quantum networks.
