Electric-field noise above a thin dielectric layer on metal electrodes

Kumph, Muir; Henkel, Carsten; Rabl, Peter; Brownnutt, Michael; Blatt, R.

doi:10.1088/1367-2630/18/2/023020

Cited by 44 publications

(61 citation statements)

References 40 publications

(82 reference statements)

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“…The exponent measured in our experiments is -1.13±0.10 which is also close to this value. Another model that fits our experimental results well is the model of a thin dielectric layer covering the electrodes [37]. It predicts the power of -4 for the trapping height dependence of the heating rate and -1 power for the frequency dependence.…”

supporting

confidence: 58%

Measuring Anomalous Heating in a Planar Ion Trap with Variable Ion-Surface Separation

2018

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Cold ions trapped in the vicinity of conductive surfaces experience heating of their oscillatory motion. Typically, the rate of this heating is orders of magnitude larger than expected from electric field fluctuations due to thermal motion of electrons in the conductors. This effect, known as anomalous heating, is not fully understood. One of the open questions is the heating rate's dependence on the ion-electrode separation. We present a direct measurement of this dependence in an ion trap of simple planar geometry. The heating rates are determined by taking images of a single 172 Yb + ion's resonance fluorescence after a variable heating time and deducing the trapped ion's temperature from measuring its average oscillation amplitude. Assuming a power law for the heating rate vs. ion-surface separation dependence, an exponent of -3.79 ± 0.12 is measured.Electric field noise in close proximity to metal surfaces is an important issue in various fields of experimental physics, such as measuring weak forces in scanning probe microscopy [1,2] or for Casimir effect studies [3, 4], gravitational wave detection [5], and experiments on the gravitational properties of charged particles [6]. In experiments with cold trapped ions such noise results in excitation (also termed heating) of the ions' motional degrees of freedom [1]. In realizations of quantum information processing based on trapped ions, this heating can become a major source of decoherence [1,8,9].Experiments have shown that the observed heating rate is orders of magnitude greater than would be caused by thermal motion of electrons in the conductors (i.e. Johnson noise) [10,11]. This high heating rate is mostly associated with surface contamination and surface imperfections, as surface treatment is known to be able to reduce the heating rate significantly [12,13]. However, its mechanism is not fully understood, and thus this effect is referred to as anomalous heating; a recent review of experimental and theoretical studies of this phenomenon is given in [1]. A comparison of experiments, employing different types and sizes of ion traps, shows that the anomalous heating rate grows fast as the ion-electrode separation decreases [1]. Therefore, anomalous heating is particularly prominent for microfabricated planar ion traps [14], where this separation can be as small as tens of micrometers. Microfabricated traps are central for the realization of scalable quantum information processing with trapped ions [14][15][16][17][18][19][20][21][22][23][24], and, therefore, in addition to its fundamental interest, it is of particular importance to characterize and understand anomalous heating.Though electric field noise-induced heating of ion motion has been studied in many experimental and theoretical works over the last years [1], one of the still open questions regarding anomalous heating is its dependence on the ion-electrode separation. In addition to being of practical use for ion trap design, knowing this dependence can confirm or contradict various existing theoret...

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confidence: 58%

Measuring Anomalous Heating in a Planar Ion Trap with Variable Ion-Surface Separation

2018

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“…Of the leading theoretical models proposed to explain anomalous ion heating, the power law scalings of the temperature dependence for the pre-ESIM measurements follow the lossy dielectric model [24] most closely. Noise, under this hypothesis, originates from the dissipative nature of any dielectric film covering the electrode metal; electric-field noise from this source is distinct from, but analogous to, the Johnson noise of a metal, though here it is based on thermally driven fluctuations in a polarizable material.…”

Section: Temperature Dependence Before and After Ion Millingmentioning

confidence: 78%

Evidence for multiple mechanisms underlying surface electric-field noise in ion traps

et al. 2018

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Electric-field noise from ion-trap electrode surfaces can limit the fidelity of multiqubit entangling operations in trapped-ion quantum information processors and can give rise to systematic errors in trapped-ion optical clocks. The underlying mechanism for this noise is unknown, but it has been shown that the noise amplitude can be reduced by energetic ion bombardment, or "ion milling," of the trap electrode surfaces. Using a single trapped 88 Sr + ion as a sensor, we investigate the temperature dependence of this noise both before and after ex situ ion milling of the trap electrodes. Making measurements over a trap electrode temperature range of 4 K to 295 K in both sputtered niobium and electroplated gold traps, we see a marked change in the temperature scaling of the electric-field noise after ion milling: power-law behavior in untreated surfaces is transformed to Arrhenius behavior after treatment. The temperature scaling becomes material-dependent after treatment as well, strongly suggesting that different noise mechanisms are at work before and after ion milling. To constrain potential noise mechanisms, we measure the frequency dependence of the electric-field noise, as well as its dependence on ion-electrode distance, for niobium traps at room temperature both before and after ion milling. These scalings are unchanged by ion milling.

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“…Neither scenario is likely to manifest on a simple metallic surface, but the trap used here has a considerably more complex structure. The combination of features like an oxide layer [31] on the aluminium-copper electrodes, adsorbates on the surface, and the influence of surface roughness [32], may allow for more complex arrangements of charges and fluctuating dipoles. The presence of an insulating layer (the oxide), for example, could separate patch potentials both above and below it, creating a structure of overlapping patches.…”

Section: A Analytic Modelmentioning

confidence: 99%

Distance scaling and polarization of electric-field noise in a surface ion trap

Matthiesen

Urban

et al. 2019

Phys. Rev. A

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We probe electric-field noise in a surface ion trap for ion-surface distances d between 50 and 300 µm in the normal and planar directions. We find the noise distance dependence to scale as d −2.6 in our trap and a frequency dependence which is consistent with 1/f noise. Simulations of the electric-field noise specific to our trap geometry provide evidence that we are not limited by technical noise sources. Our distance scaling data is consistent with a noise correlation length of about 100 µm at the trap surface, and we discuss how patch potentials of this size would be modified by the electrode geometry.

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Electric-field noise above a thin dielectric layer on metal electrodes

Cited by 44 publications

References 40 publications

Measuring Anomalous Heating in a Planar Ion Trap with Variable Ion-Surface Separation

Measuring Anomalous Heating in a Planar Ion Trap with Variable Ion-Surface Separation

Evidence for multiple mechanisms underlying surface electric-field noise in ion traps

Distance scaling and polarization of electric-field noise in a surface ion trap

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