An ion crystal quantum repeater – Niels Bohr Institute - University of Copenhagen

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An ion crystal quantum repeater

An important goal of quantum information science is reliable quantum communication. This is a serious challenge given the rapid decoherence of quantum systems. A possible way forward is to use so-called quantum repeaters to distribute entanglement between the sender and the receiver and a promising scheme is the DLCZ repeater (1) which uses ensembles of atoms for the entanglement distribution. Ion Coulomb crystals (2) are attractive ensembles for the DLCZ repeater since they have the potential to be good quantum memories and they couple well to light when put in an optical cavity.


In this master's thesis defence we present a detailed calculation of the quantum repeater's so-called write-in interaction in an ion crystal in a standing wave cavity. The combination of the standing wave and the thermal movement of the individual ions is shown to destroy the write-in. A possible solution to the problem is given in the form of moving the whole crystal during the interaction with light. Then, we calculate the so-called read-out interaction and again try to solve the problem of the standing wave by fast displacement of the crystal.