Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 2: Quanteninformation (Atome und Ionen I)
Q 2.4: Talk
Monday, March 10, 2008, 15:00–15:15, 1B
Deterministic Entanglement Swapping with Trapped Ions — •Mark Riebe1, Thomas Monz1, Kihwan Kim1, Alessandro Villar2, Philipp Schindler1, Markus Hennrich1, and Rainer Blatt1,2 — 1Institut für Experimentalphysik, Universität Innsbruck, Austria — 2Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Austria
Entanglement is a key feature in the field of quantum information processing, as it allows for quantum communication, secret key sharing and quantum computation. Many of these applications require entangled states distributed among distant locations. Distribution of entangled states can be aided by a scheme known as entanglement swapping [1]. We demonstrate this scheme with a string of four trapped 40Ca-ions, which carry quantum information in their internal states S1/2 and D5/2 [2]. Initially, ion pairs 1,2 and 3,4 are each prepared in the Bell state Ψ−=(|DS⟩−|SD⟩)/√2. Then, ion 1 and 4 are measured in the Bell basis. The result of this measurement is perfectly correlated with the Bell state into which the previously unentangled ions 2 and 3 are projected. We make use of this fact and apply further rotations to ion 3 conditioned by the Bell measurement result, such that ions 2 and 3 are deterministically mapped to the state Ψ−. This is confirmed by determining the final state of ions 2,3 by state tomography, which proves that we prepare the state Ψ− with a fidelity of 79%.
[1] J. W. Pan et al., Phys. Rev. Lett. 80, 3891 (1998).
[2] F. Schmidt-Kaler et al., Appl. Phys. B 77, 789 (2003).