Single trapped ions interacting with low‐ and high‐finesse optical cavities

Abstract

The presence of mirrors modifies both the coherent coupling of an atom to a light mode and its spontaneous emission into the mode [1]. We study such cavity QED effects experimentally with single ions and optical cavities. We focus on two examples which are equally interesting as fundamental systems and for application in quantum information processing. (i) By retroreflecting the fluorescence of a single trapped Ba+ ion with a mirror 25 cm away, we observe inhibition and enhancement of the atom's spontaneous emission. When two ions are trapped, the distant mirror creates super‐ and subradiance. (ii) With a single trapped Ca+ ion we demonstrate coherent coupling of its narrow S1/2 – D5/2 “qubit” transition to a mode of a high‐finesse optical cavity. We also achieve deterministic coupling of the cavity standing wave to the ion's vibrational state by controlling the ion's position with nanometer‐precision and selectively exciting vibrational state‐changing transitions.

About the Exact Role of Disturbance in Heisenberg's Uncertainty Relation

“…The way to confine the single ion even more is by introducing an optical cavity, thereby introducing cavity Quantum Electro Dynamics (QED). Recent work from Gulde et al [39] (Section 2.2.2) reports about a localization down to 7 nm for the ions in a one-dimensional lattice and Eschner et al [40] (p. 367) reports about a confinement of 6 nm, and that in axial direction for both publications. Thanks to the ioncavity mode coupling the ion(s) can be exactly positioned with nm accuracy.…”

Integrated Optical Approach to Trapped Ion Quantum Computation

“…Cavities constructed around the ion can substantially modify the spontaneous emission properties of the ions, and make the photon collection process dramatically more efficient [10,63,64,65]. In a recent experiment, a high quality factor (Q) cavity was constructed around a trapped ion and deterministic state evolution between the ion and a single cavity photon was demonstrated with an estimated single photon generation efficiency of ∼ 8% and photon detection efficiency of ∼ 4.6% (overall yield of ∼ 0.4% for detecting single photon when the ion is excited) [66].…”

Multipartite entanglement of three trapped ions in a cavity and W-state generation

“…[10] and the decoherence process of this three qubit system examined [11]. Experimentally successful efforts in this direction [12,13,14], have demonstrated coherent coupling of electronic and motional states of a single trapped Ca + ion to single field mode of a high finesse cavity. In the experiment of ref.…”

“…A different scheme to generate the three qubit maximally entangled GHZ state, using a trapped ion interacting with a resonant external laser and sideband tuned single mode of a cavity field has been proposed in [10] and the decoherence process of this three qubit system examined [11]. Experimentally successful efforts in this direction [12][13][14] have demonstrated coherent coupling of electronic and motional states of a single trapped Ca + ion to a single field mode of a high finesse cavity. In the experiment of [12], a Ca + ion in an RF-Paul trap was placed with high precision at an arbitrary position in the standing wave field of a near-confocal resonator for several hours of interaction time.…”

“…With the cavity prepared initially in a Fock state, the entanglement of ionic internal states depends strongly on the choice of the phonon number at t = 0. Extra control on qubit state manipulation, gained by coupling the vibrational modes to the cavity field [13,14], is an advantage for the successful implementation of quantum gates.…”