“The conventional optical fibers that form the backbone of today’s telecommunications networks transmit light at wavelengths determined by the losses of silica glass,” says Dr. Kristina Rusimova from the Department of Physics at the University of Bath. “However, these wavelengths are incompatible with the operational wavelengths of single-photon sources, qubits, and active optical components essential for light-based quantum technologies.”

Enter the microstructured optical fiber. Unlike traditional optical fibers with solid glass cores, these new fibers feature a complex pattern of air pockets running along their entire length. This seemingly simple change unlocks a myriad of possibilities for controlling and manipulating light in ways crucial for quantum technologies. One of the most exciting applications of these fibers is in creating the building blocks of a quantum internet. By carefully designing the structure of these fibers, researchers can generate pairs of entangled photons—particles of light that remain inextricably linked regardless of the distance between them. This quantum entanglement is the essential ingredient that enables many quantum technologies.

“A quantum internet is vital for realizing the vast promises of emerging quantum technology. Much like the existing internet, a quantum internet will rely on optical fibers to transmit information from node to node,” says Dr. Cameron McGarry, first author of the paper. “These optical fibers will differ significantly from those currently in use and will require different supporting technologies to be effective.”

But the potential of these fibers extends beyond just transmitting quantum information. They could also play a crucial role in quantum computation. Dr. McGarry explains, “The pattern of these air pockets allows researchers to manipulate the properties of light inside the fiber, create entangled photon pairs, change the color of photons, or even trap individual atoms inside the fibers.”

This versatility means that microstructured fibers could serve multiple functions in a quantum network. They could act as sources of entangled photons, convert between different wavelengths of light (essential for connecting different types of quantum systems), function as low-loss switches, or even serve as quantum memories.

“The ability of fibers to tightly confine light and transport it over long distances makes them incredibly useful,” says Dr. Alex Davis, an EPSRC Quantum Career Acceleration Fellow at Bath. “In addition to generating entangled photons, this allows us to produce more exotic quantum states of light with applications in quantum computing, precision sensing, and impregnable message encryption.”

By Impact Lab