Probing surface charge densities on optical fibers with a trapped ion

Abstract

We describe a novel method to measure the surface charge densities on optical fibers placed in the vicinity of a trapped ion, where the ion itself acts as the probe. Surface charges distort the trapping potential, and when the fibers are displaced, the ion's equilibrium position and secular motional frequencies are altered. We measure the latter quantities for different positions of the fibers and compare these measurements to simulations in which unknown charge densities on the fibers are adjustable parameters. Values ranging from −10 to +50 e/µm 2 were determined. Our results will benefit the design and simulation of miniaturized experimental systems combining ion traps and integrated optics, for example, in the fields of quantum computation, communication and metrology. Furthermore, our method can be applied to any setup in which a dielectric element can be displaced relative to a trapped charge-sensitive particle.

Industrially Microfabricated Ion Trap with 1 eV Trap Depth

“…The data in Figure 4b (lines) are fitted to the simulated field from uniform charge densities on these sidewalls, producing values up to 2500 elementary charges per µm 2 (Table 2). This is larger than the charge densities reported on fiber surface near ions [65] and on a planar trap [63], but these materials and geometries may not be comparable. The model uses seven free parameters: a uniform charge density on each of the spacers 1-4 that control field curvature along the axis, and the three components of a constant, arbitrary field E offset that set the offset.…”

“…The magnitude of field components in both traps is similar to many single-wafer surface traps [19,30,43,46,[59][60][61][62] made from a variety of materials and measured at different temperatures and ion-surface distances. Proposed sources of such fields include charge present on dielectric or metal surfaces [63][64][65], as well as patch potentials comprising surface oxides [49,66] or adsorbates [67][68][69]. These sources can contribute to field offsets if they are distant or distributed, or to field curvature if they are close and point-like.…”

“…In one such case, a significant change in measured field occurred after DC electronics were disconnected and reconnected. This could have possibly reconnected floating electrodes (thus changing the calibration of applied compensation or affecting the charge state of weakly implanted electrons in dielectric close to the electrodes [65]) or changed the contact potential at a conductor interface. We note that after the jump the compensated field drift was observed to reverse direction.…”

Heating of a trapped ion induced by dielectric materials

“…Excluding the point corresponding to the shortest distance of d = 250 µm results in a value of χ 2 ν = 0.86, demonstrating strong agreement. At this short distance, the axial trapping potential is significantly influenced by inhomogeneously distributed surface charges, which, however, are not considered in the simulations [38]. Potentially, more information could be extracted by measuring a frequency scaling similar to that of Fig.…”

Precise and extensive characterization of an optical resonator for cavity-based quantum networks

“…No significant mechanical modes are found below 20 kHz, which would be helpful for stabilizing the cavity frequency. Our method could be exploited for characterizing not only the cavities for atomor ion-based quantum networks [26,45,47,48], but also other Fabry-Pérot cavities in which fundamental quantum optics [49], precision measurement [50], and manybody physics are investigated [51][52][53].…”