As if plain old quantum entanglement weren’t strange enough for modern physics, now physicists are entangling already entangled particles. In entanglement swapping, one particle of an entangled pair becomes entangled with a third particle, which itself becomes entangled with the other particle in the first pair, even though the two never interact. Here’s how physicists are unraveling this behavior and manipulating it for use in quantum communications and high-speed computing.
Even as today’s most powerful supercomputers can send information at ever increasing speeds, scientists predict that quantum computers will operate millions of times faster. With the help of entangled photons, which instantaneously correlate with one another even when separated by large distances, scientists are developing a process called quantum teleportation. Currently, however, physicists can only teleport information a hundred or so miles before signal loss weakens the connection.
With a quantum repeater – containing an independent, synchronized photon source – located at periodic locations along the channel, a computational signal will receive a power boost, enabling it to continue toward its destination. In a sense, entanglement swapping is a bit like fueling your car at a gas station – but you can skip all the driving in between.