Scientists are working on building a quantum internet, with quantum memories being a crucial component. These memories store fragile quantum information and are essential for creating quantum networks that can enable secure messaging and connecting distant quantum computers. Establishing entanglement throughout a network is a key goal of these memories, allowing for quantum connections to be made.
Two teams of scientists have successfully entangled quantum memories in networks within cities, facing the challenges of urban environments in quantum communications. These studies mark a significant milestone as they move quantum systems from the lab to real-world implementations. The research involved a network of two quantum memories connected through a telecommunications fiber link in Boston and Cambridge. The entanglement was maintained for about a second, which is considered a long time in the quantum realm.
The quantum memories used in the research consisted of diamonds with a silicon atom defect serving as a qubit. This allowed scientists to entangle two memories by sending photons through a fiber link. In a separate study in Hefei, China, entanglement was achieved in a network with three quantum memories using rubidium atoms as a qubit source. The method involved measuring photons in a central station, generating entanglement between distant parts of the network and avoiding the need for photons to travel extensively.
Researchers faced challenges such as achieving phase stabilization to correct for fiber length changes due to temperature shifts in the Hefei network. The Boston network, on the other hand, did not require central stations or phase stabilization. Both teams successfully achieved heralded entanglement, confirming the establishment of entanglement long enough for information to traverse the network. This achievement is crucial for practical applications of quantum networks.
The differences in approaches between the two teams highlight the promising variety in quantum communication methods. The successful establishment of heralded entanglement in both studies demonstrates progress towards developing functioning quantum networks for future applications. Quantum internet technology is advancing towards more practical implementations, bringing quantum communications out of theoretical research labs and into the real world.
