One of the challenges that physicists face in creating a quantum Internet is to distribute entangled photons around the planet. The idea is that a user in Tokyo could use this entanglement to send a perfectly secure message to somebody in Moscow or Johannesburg or New York.
The problem is that entangled photons are difficult to send over these distances because optical fibers absorb then. This process of absorption limits the distance that physicists can distribute entanglement to about 100 kilometers.
One solution is to place quantum repeaters along a fiber that pass on the entanglement without destroying it. Physicists are currently developing these kinds of devices and expect to have them operating in the next few years.
However, quantum repeaters will operate at temperatures close to absolute zero and require their own power and cooling infrastructure. That is all possible on land but is much harder to make work for transoceanic cables. Which is why physicists are looking for alternative ways to distribute entanglement over long distances.
Today, Kristine Boone at the University of Calgary in Canada and a few pals outline a plan to distribute entanglement around the planet from satellites orbiting a couple of hundred kilometers above the Earth. “Our proposed scheme relies on realistic advances in quantum memories and quantum non-demolition measurements and only requires a moderate number of satellites equipped with a tangled photon pair sources,” they say.
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