Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 2: Quanteninformation (Atome und Ionen I)
Q 2.5: Talk
Monday, March 10, 2008, 15:15–15:30, 1B
Three-qubit Toffoli gate with trapped ions — •Thomas Monz1, Kihwan Kim1, Wolfgang Hänsel1, Alessandro Villar2, Philipp Schindler1, Mark Riebe1, Markus Hennrich1, and Rainer Blatt1,2 — 1Institut für Experimentalphysik, Universität Innsbruck, Austria — 2Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Austria
Quantum algorithms are usually decomposed into a sequence of gate operations each acting only on a few qubits. A well-known set for this purpose is a two-qubit controlled NOT (CNOT) gate combined with single qubit rotations. However, gates that connect more than two qubits could facilitate quantum computations. One example is the three-qubit Toffoli gate, which is a valuable tool for quantum error correction. The Toffoli gate acts on a register of two control qubits |c1,c2⟩ and one target qubit |t⟩ as |c1,c2,t⟩→|c1,c2,(c1∧ c2)⊕ t⟩. We implement this gate with a string of trapped ions, where we use the ion’s internal states as qubits and manipulate these with suitable laser pulses. Our implementation relies on an extension of the Cirac-Zoller gate proposal [1]: First a carefully designed sequence of laser pulses encodes the information (c1∧ c2) in one of the ion string’s vibrational modes. Then a CNOT gate between the target qubit and the vibrational mode realizes the operation |t⟩→|(c1∧ c2)⊕ t⟩. Finally, the initial encoding procedure is reversed. We analyze the Toffoli gate operation by quantum process tomography, and obtain a mean gate fidelity of 79%.
[1] J. I. Cirac and P. Zoller, Phys. Rev. Lett. 74, 4091 (1995).