Longest Quantum Internet Demonstrated in Boston

Harvard researchers have demonstrated quantum internet communication over the longest distance achieved to date using existing telecommunication cables in Boston, Massachusetts.

The physicists entangled two quantum memory nodes across a 22-mile optical-fiber loop connecting Cambridge, Somerville, Watertown and Boston.

The demonstration used the quantum property of entanglement, in which linked quantum particles, in this case photons, contain the same information even if they are miles apart.

A quantum internet holds the promise of hacker-proof communications and even connecting remote quantum computers into a single, more powerful machine.

Compared with previous quantum internet experiments, Harvard’s demonstration connected nodes that can store, process and move information over a longer fiber network.

In this case, the nodes were silicon-vacancy diamond slivers that act as a tiny quantum computer. This vacancy can contain two qubits, one used for communication and the other for memory to store the entanglement state.

“Since the light is already entangled with the first node, it can transfer this entanglement to the second node,” said one of the paper’s authors, Harvard researcher Can Knaut. “We call this photon-mediated entanglement.”

The team leased the optical fiber from a local company, fitting their demonstration network on top to demonstrate the feasibility of using a similar setup in a real-world environment. 

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The team plans to extend the network and add further nodes for the next stage of research.