Finite-geometry models of electric field noise from patch potentials in ion traps

Low, Guang Hao; Herskind, Peter F.; Chuang, Isaac L.

doi:10.1103/physreva.84.053425

Cited by 35 publications

(56 citation statements)

References 38 publications

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“…This power law is consistent with the patch potential model [1,10,36] in the limit of small patches. The frequency dependence of the heating rate can be different depending on the mechanism behind the patch potential fluctuations.…”

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confidence: 67%

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: 67%

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

2018

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“…The data are also consistent with a d −4 scaling law (where d is the distance from the ion to the nearest electrode), as would be predicted for a random distribution of fluctuating charges or dipolar patch potentials on the surface (for Johnson noise, a d −2 scaling law would be expected) [52][53][54]. Theoretically, a correlation length associated with surface disorder has been shown to characterize electric field noise generated near the surface [53,55] and microscopic models have been developed based on fluctuations of the electric dipoles of adsorbed molecules [54,56]. However, the predictions of available noise models are not in agreement with recent measurements [57].…”

Section: Mitigating Motional Decoherencesupporting

confidence: 65%

Technologies for trapped-ion quantum information systems

Eltony

Gangloff

Shi

et al. 2016

Quantum Inf Process

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Scaling up from prototype systems to dense arrays of ions on chip, or vast networks of ions connected by photonic channels, will require developing entirely new technologies that combine miniaturized ion trapping systems with devices to capture, transmit, and detect light, while refining how ions are confined and controlled. Building a cohesive ion system from such diverse parts involves many challenges, including navigating materials incompatibilities and undesired coupling between elements. Here, we review our recent efforts to create scalable ion systems incorporating unconventional materials such as graphene and indium tin oxide, integrating devices like optical fibers and mirrors, and exploring alternative ion loading and trapping techniques.

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“…In addition to static fields, surfaces may also be a source of enhanced fluctuating fields, a problem which plagues ion-trapping (see Ref. [24] and references therein) and is also a consideration for Rydberg atoms near surfaces [12]. For dielectrics, which are a necessary part of any non-trivial device -as insulating gaps for instance -charging and time-dependent electric fields due to adsorbates [7] must also be considered.…”

Section: Introductionmentioning

confidence: 99%

Electric-field sensing near the surface microstructure of an atom chip using cold Rydberg atoms

2012

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This thesis reports experimental observations of electric fields using Rydberg atoms, including dc field measurements near the surface of an atom chip, and demonstration of measurement techniques for ac fields far from the surface. Associated theoretical results are also presented, including Monte Carlo simulations of the decoherence of Rydberg states in electric field noise as well as an analytical calculation of the statistics of dc electric field inhomogeneity near polycrystalline metal surfaces.DC electric fields were measured near the heterogeneous metal and dielectric surface of an atom chip using optical spectroscopy on cold atoms released from the trapping potential. The fields were attributed to charges accumulating in the dielectric gaps between the wires on the chip surface. The field magnitude and direction depend on the details of the dc biasing of the chip wires, suggesting that fields may be minimized with appropriate biasing.Techniques to measure ac electric fields were demonstrated far from the chip surface, using the decay of a coherent superposition of two Rydberg states of cold atoms. We have used the decay of coherent Rabi oscillations to place some bounds on the magnitude and frequency dependence of ac field noise.The rate of decoherence of a superposition of two Rydberg states was calculated with Monte Carlo simulations. The states were assumed to have quadratic Stark shifts and the power spectrum of the electric field noise was assumed to have a power-law dependence of the form 1/f κ . The decay is exponential at long times for both free evolution of the superposition and and Hahn spin-echo sequences with a π refocusing pulse applied to eliminate the effects of low-frequency field noise. This decay time may be used to calculate the magnitude of the field noise if κ is known.The dc field inhomogeneity near polycrystalline metal surfaces due to patch potentials on the surface has been calculated, and the rms field scales with distance to the surface as 1/z 2 . For typical evaporated metal surfaces the magnitude of the rms field is comparable to the image field of an elementary charge near the surface.iii Acknowledgements I would first like to thank my supervisor, Dr. James Martin, for his hard work, dedication, and assistance through this project. I'd also like to thank Dr. Martin for reading the drafts of this thesis and making many helpful comments and suggestions.Thanks to Owen Cherry, my colleague during the initial phase of this project. Owen fabricated the atom chips described in this work and was involved in the assembly of the vacuum chamber and the MOT optics.

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Finite-geometry models of electric field noise from patch potentials in ion traps

Cited by 35 publications

References 38 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

Technologies for trapped-ion quantum information systems

Electric-field sensing near the surface microstructure of an atom chip using cold Rydberg atoms

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