Saturday science subject: Quantum teleportation

Slowly but surely, researchers seem to be inching toward workable quantum computers. According to IEEE Spectrum, Christopher Monroe and his team at the University of Maryland may have gotten one step closer: they've teleported the quantum state of an ion to another ion a meter (3.3 ft) away.

Quantum teleportation isn't entirely new, but Monroe says his particular approach "will enable the creation of quantum repeaters—still-theoretical devices needed to make large-scale quantum cryptography networks—and will also be useful for making quantum computers." IEEE Spectrum has more:

At the heart of teleportation lies a quantum mechanics effect known as entanglement. That phenomenon allows two particles—such as photons, atoms, or ions—to be linked in such a way that if someone measures the quantum state of one object, the state of the other becomes known as well. Entangled photons are often used in experimental quantum information networks. But while photons are easy to transmit (after all, they move with the highest speed in the universe), they are very difficult to store. On the other hand, atoms and ions preserve entanglement for a long time, but being massive, they are much harder to move from place to place.

The beauty of Monroe's approach to teleportation is that it is an intelligent combination of the strengths of photons and ions. His team used two ytterbium ions confined in electromagnetic ion traps and cooled by lasers. The goal is to teleport the quantum state of one ytterbium ion to the other. Both ions are prepared for entanglement by microwave pulses and then zapped by ultrafast laser pulses. Each ion subsequently gives off a photon, which is entangled with the ion's state. Through a complex series of steps, the system transfers the quantum state of one ytterbium ion to the other.

Although he and his team have only demonstrated teleportation across one meter, Monroe says that in theory, his approach "can be extended to distances as great as thousands of kilometers."

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