Expanding Horizons of Long-Haul Quantum Communications

Since quantum teleportation first became a reality 25 years ago, scientists have pushed its limits. Teleportation—outside the Star Trek universe—consists of transmitting a quantum state from one system to another via quantum entanglement. The two quantum systems (two atoms in a laser trap) can be right next to one another, or they can be separated by arbitrarily large distances. Strange as it sounds, quantum teleportation has been widely observed in the lab and even harnessed in emerging quantum technologies. To date, scientists have achieved quantum teleportation across distances as great as 1,400 kilometers. Yet there are other kinds of limitations than physical distance. Until now, quantum teleportation could only happen between, say, atoms that had been in direct contact with each other.