Building long-range quantum networks is one of the most important and ambitious goals of quantum science and engineering. To connect these networks into a quantum internet will require intermediate stations where quantum information—carried by photons—can be manipulated and “refreshed.” These stations, known as quantum repeaters, contain long-lived qubits with an optical interface that allows the photons to be entangled with the spins encoding these qubits. Color centers in solids are prime candidates for quantum repeaters, as they can have long coherence times, spin-selective optical transitions, and compatibility with photonic devices, such as cavities, that facilitate photon emission and routing. The tin-vacancy (SnV) center in diamond, a relatively new and promising color center , features several of these key elements. Until recently, however, these SnV centers had not been integrated into cavities in which their emission would be enhanced. Now, a team led by Jelena Vučković at Stanford University has succeeded in integrating an SnV center into a nanophotonic device and has achieved 90% photon emission into the desired cavity mode . This work is an important step toward the realization of long-range quantum networks.
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