Long-lived mesoscopic entanglement outside the Lamb-Dicke regime

Abstract

We create entangled states of the spin and motion of a single ${}^{40}$Ca${}^{+}$ ion in a linear ion trap. The motional part consists of coherent states of large separation and long coherence time. The states are created by driving the motion using counterpropagating laser beams. We theoretically study and experimentally observe the behaviour outside the Lamb-Dicke regime, where the trajectory in phase space is modified and the coherent states become squeezed. We directly observe the modification of the return time of the trajectory, and infer the squeezing. The mesoscopic entanglement is observed up to $\Delta \alpha =5.1$ with coherence time 170 microseconds and mean phonon excitation $\nbar = 16$.

5 pages, 3 figures. Revised version after editor comments

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• Quantum information with continuous variables
• Scalable multi-particle entanglement of trapped ions
• Entanglement of a Mesoscopic Field with an Atom induced by Photon Graininess in a Cavity
• Isotope-selective photo-ionization for calcium ion trapping
• Spin-dependent forces on trapped ions for phase-stable quantum gates and motional Schrodinger-cat states
• Quantum mechanical counterpart of nonlinear optics

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