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Quantized phase shifts and a dispersive universal quantum gate

F. Schmidt-Kaler·H. Haeffner·S. Gulde·M. Riebe·G. Lancaster·J. Eschner·C. Becher·R. Blatt
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Abstract

A single 40Ca+ 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 |n>. 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 |n>={|0>,|1>}. 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.

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F. Schmidt-Kaler, H. Haeffner, S. Gulde, M. Riebe, G. Lancaster, J. Eschner, C. Becher, R. Blatt. 2003-07-29. Quantized phase shifts and a dispersive universal quantum gate. https://arxiv.org/abs/quant-ph/0307211

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