Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 6: Quanteninformation (Atome und Ionen II)
Q 6.3: Talk
Monday, March 10, 2008, 17:00–17:15, 1B
Realization of decoherence-free ion trap quantum computation — •Kihwan Kim1, Thomas Monz1, Alessandro Villar2, Philipp Schindler1, Michael Chwalla1, Mark Riebe1, Markus Hennrich1, Wolfgang Hänsel1, and Rainer Blatt1,2 — 1Institut für Experimentalphysik, Universität Innsbruck, Austria — 2Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Austria
Quantum computation is limited by decoherence from technical noise and coupling of the qubits to the environment. However, certain states were shown to be protected from decoherence due to their symmetry [1]. These states form a decoherence-free subspace (DFS) of the Hilbert space. Using the DFS as a robust computational space will help to realize large scale quantum computing. In this talk we show the first realization of a universal set of gate operations in a DFS with ion strings. We use trapped 40Ca ions and store quantum information in the ion’s electronic states S1/2 and D5/2. A DFS is formed by the two states |SD⟩ and |DS⟩ which are used as logical qubits |0L⟩ and |1L⟩. In this DFS, single-qubit rotations are realized using a Mølmer-Sørensen gate between the two ions of the logical qubit. For two-qubit operations between logical qubits a σz-type geometric phase gate is applied to neighbouring ions of two adjacent logical qubits [2]. We obtain fidelities of around 94% for a single qubit π/2-rotation and around 75% for a CNOT gate in DFS.
[1] D. Kielpinski et al., Nature 417, 709 (2002).
[2] L. Aolita et al., Phys. Rev. A 75, 052337 (2007).