Search for correlation effects in linear chains of trapped Ca ⁺ ions

Abstract

We report a precise search for correlation effects in linear chains of 2 and 3 trapped Ca + ions. Unexplained correlations in photon emission times within a linear chain of trapped ions have been reported, which, if genuine, cast doubt on the potential of an ion trap to realize quantum information processing. We observe quantum jumps from the metastable 3d 2 D 5/2 level for several hours, searching for correlations between the decay times of the different ions. We find no evidence for correlations: the number of quantum jumps with separations of less than 10 ms is consistent with statistics to within errors of 0.05%; the lifetime of the metastable level derived from the data is consistent with that derived from independent single-ion data at the level of the experimental errors (1%); and no rank correlations between the decay times were found with sensitivity to rank correlation coefficients at the level of |R| = 0.024.

Lifetime measurement of the metastable3dD5∕22state in theStaanum1, Jensen2, Martinussen3 et al. 2004Phys. Rev. A304211View full textAdd to dashboardCite

“…[3], which together with other recent results are presented in Table II. On the level of two standard deviations, our result agrees with two other measurements where deshelving due to diode lasers was taken into account [8,14] and with the storage-ring measurement by Lidberg et al [9] (see Table II). Furthermore, our result agrees with two theoretical values [16,17].…”

“…In the experiments by Block et al [8] indications of correlated decays from the 2 D 5/2 state were observed, manifested as an overrepresentation of events where several ions decay at the same time. A later detailed experiment by Donald et al [14] showed, however, no such correlations. Apart from sudden bursts of 854 nm radiation, the only reasonable physical mechanism which could lead to correlations is so-called subradiant and superradiant spontaneous emission due to inter- ference in the spontaneous decay of two or more ions [26].…”

Tests for nonrandomness in quantum jumps

“…This, too, is consistent with the behavior of the ions being random, and agrees with the results of Ref. [14].…”

Simplified approach to double jumps for fluorescing dipole-dipole interacting atoms

“…On the other hand, experiments with different ions showed no observable cooperative effects [11], in particular none were seen for Hg + for a distance of about 15 wave lengths [12]. More recently, effects similar to reference [3] were found in an experiment with Ca + ions [13], in contrast to another, comparable, experiment [14]. Neither were cooperative effects found experimentally in an extensive analysis of the quantum jump statistics of two trapped Sr + ions [15].…”