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Hansonlab demonstrates quantum teleportation

Researchers in the lab of Ronald Hanson have demonstrated the teleportation of information between two entangled quantumbits three metres apart. Science online published their article today.

The cellar of the old physics building houses a delicate setup of two cryostats, lasers, semitransparent mirrors and microwave equipment. In the cryostat, at about 270 degrees Celsius subzero, lasers are focused on a small diamond strip with a tiny lens on top. A single electron spin in the diamond lattice functions as a quantumbit.

Last year the researchers of the Kavli institute of nanoscience at TU’s Applied Sciences faculty have demonstrated the entanglement of two such quantumbits separated by three meters across the lab.

Entanglement is a weird quantummechanical property that encapsulates two particles in one wave function, irrespective of their distance. What happens to one of the particles has immediate consequences for the other.

A year later, the team has used much the same equipment to actually send information from one cryostat to the other.

Hanson explains the procedure in a neat video. Suppose two distant quantumbits (qubits) B and C are entangled. Next to B, there is another qubit A whose quantum state we want to teleport. A smart measurement is then performed on A and B, which entangles them and transfers A’s quantum state onto C. In the process however the information gets distorted and additional information is needed to reconstruct A’s original state. Hanson compares this additional information to a rotation (clockwise, anti-clockwise, upside-down or no rotation)).

And although the transfer of information from A to C is immediate, which seems to violate the laws of physics, the transfer of the additional information occurs by conventional ways of communication. This implies that information transfer by teleportation is not at odds with the laws of physics.

In the Science article Hanson and colleagues claim a 86 percent reliability in information transfer.

Rather than beaming up objects and people, the researchers think of applications in secure quantum networks and information exchange between small processors in the future quantum computer.

→ Wolfgang Pfaff, Bas Hensen, Hannes Bernien e.a. & Ronald Hanson, Unconditional quantum teleportation between distant solid-state qubits, Science online, 29 May 2014

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