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Probabilistic entanglement creation in distant atoms

Final Activity Report Summary - PECADO (Probabilistic entanglement creation in distant atoms)

In the future, quantum-entangled states of distant atoms will play an essential role for quantum networking and quantum communication. For example, it will be possible to build a non-local quantum computer, where the entangled state links two quantum processors formed by two ion strings in two distant traps. In another vision, the entanglement can be used to teleport the internal atomic state of an atom in one trap to an atom in a second, remote trap. Within this project, a first step towards implementing these visions was taken.

The main project achievement was the set-up of a quantum optical experiment for the creation of entangled, distant atoms. The main ingredients of the highly complex system were:
1. two ion trap assemblies which held individual atoms and allowed for their interaction with laser pulses;
2. the lasers which would be used to manipulate these single atoms; and
3. the detection devices which would permit the creation and observation of entanglement between the atoms.

As a classical system, the experiment consisted by a very large interferometer where a laser pulse was split, passed through a single atom in each arm and then was combined and detected. In the quantum picture, this detection led to the entanglement between the atoms.

Our experimental set-up was close to operation; once ions were trapped, we would initially demonstrate interference of their fluorescence, i.e. of the scattered laser pulse. Stable interference was required so that the generated state possessed useful entanglement properties. In later steps this entanglement and its dynamics would be characterised before being used for first applications of teleportation and quantum networking.