Europhys. Lett.
Volume 65, Number 5, March 2004
Page(s) 587 - 593
Section General
Published online 01 February 2004
Europhys. Lett., 65 (5) , pp. 587-593 (2004)
DOI: 10.1209/epl/i2003-10174-3

Quantized AC-Stark shifts and their use for multiparticle entanglement and quantum gates

F. Schmidt-Kaler, H. Häffner, S. Gulde, M. Riebe, G. Lancaster, J. Eschner, C. Becher and R. Blatt

Institut für Experimentalphysik - 6020 Innsbruck, Austria

(Received 5 September 2003; accepted 18 December 2003)

A single $\chem{{}^{40}Ca^{+}}$-ion is trapped and laser-cooled to its motional ground state. Laser radiation which couples off-resonantly to a motional sideband of the ion's S1/2 to D5/2 transition causes a phase shift proportional to the ion's motional quantum state $\vert n\rangle$. As the phase shift is conditional upon the ion's motion, we are able to demonstrate a universal 2-qubit quantum gate operation where the electronic target state $\{S,D\}$ is flipped depending on the motional qubit state $\vert n\rangle=\{\vert\rangle, \vert 1\rangle\}$. Finally, we discuss scaling properties of this universal quantum gate for linear ion crystals and present numerical simulations for the generation of a maximally entangled state of five ions.

03.67.Lx - Quantum computation.
03.65.Ud - Entanglement and quantum nonlocality (e.g., EPR paradox, Bell's inequalities, GHZ states, etc.).

© EDP Sciences 2004