Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Berkeley Scientific Journal

Fourier Transform Infrared Analysis of Surface Ion Traps - eScholarship

William Tokumaru, Ishan Talukdar, Harmut Haeffner

Published Jan 1, 2016• 0 citations
OpenAlex

Abstract

FOURIER TRANSFORM INFRARED ANALYSIS OF SURFACE ION TRAPS Abstract: This study examines gold and copper-aluminum surfaces in air and vacuum via Fourier-transform in- frared spectroscopy to learn more about the causes of electric surface noise in ion traps. The FTIR spectra show traces contamination, including unique fingerprints in the range of 4000 to 600 cm-1. We study how the spec- tra change when the surfaces are exposed to controlled hydrocarbon contamination. We also study wheth- er procedures commonly used in ion trapping such baking for establishing ultra-high vacuum, and exposure to blue to ultraviolet light radiation alter the surface. Spectra of individual surfaces are found to differ more from each other than they do under these procedures. This work is based off of the first author’s honors thesis. BY WILLIAM TOKUMARU, ISHAN TALUKDAR, & HARTMUT HAEFFNER LAYOUT BY ELLIS VAVRA, REBECCA CHAN, AVANI VAID, HYEONJI SHIM, HARRISON RAMSAY INTRODUCTION AND BACKGROUND Quantum computing has exciting applications ranging from clever solutions for optimization problems to superior im- plementations of existing algorithms. [1] It should enable cracking of traditional cryptography, while likewise protecting infor- mation. One of the most promising ways to create a universal quantum computer is using trapped ions. [1] While quantum computing with trapped ions is well advanced, surface noise prevents progress towards smaller and more compact systems which would allow for faster and more flexible quantum computing architectures. [2, 3] Ion “qubits” are controlled by manipulating electronic and motional states of ions with lasers. Unfortunately, electric field noise limits the coherence of multi-qubit operations by destroying the quan- tum information in the quantum bus connecting the respective qubits. [2] After eliminating technical noise, the remaining noise is too large to be explained by Johnson noise and unlikely to be a systematic or a measurement error. Instead, the noise has been reduced by cooling the electrodes to cryogenic temperatures, by increasing the distance of the ions from the surfaces, and by surface treatment with energetic Argon ions. Concentrated laser radiation has been reported to both decrease and increase heat- ing rates. [4-10] In particular, surface treatment experiments suggest that surface contaminants play an important role in the observed noise. [6] Indeed, Auger electron spectroscopy shows that carbon and oxygen are present before treatment and are removed by the energetic Argon ions. [7, 8] However, the experiments in Ref. [8] also report that subsequent re-contamination from molecules present in Ultra-High Vacuum (UHV) does not let the noise reappear. Carbon contamination may be either in the form of atomic carbon or of hydrocarbons deposited on the electrodes somewhere during the fabrication, assembly or baking proce- dures. The studies in this paper aim at comprehending the noise mechanisms to help in future experimental planning. They also apply to numerous other fields studying electric noise near surfaces, including engineering nanoelectronics and supercon- ducting electronics, detection of Casimir forces in quantum field theory, tests of general relativity, and hybrid quantum devices. Organic materials present in air tend to adsorb onto metal and form nanostructures to reduce the free energy be- tween surfaces and the environment. [16] A common model for these contaminants is based around Self-assembled Monolayers (SAMs). [17] These molecular structures are formed from exposure to fluids and gases with organic content and organize sponta- neously into crystalline-like adatom structures. They commonly appear on gold and copper surfaces, both of which are common traps electrode materials. [18-27] Many SAMs are “alkanethiols,” FALL 2016 | Berkeley Scientific Journal

Related papers

Treatments of a Surface Ion Trap: A Study of Electric-Field Noise near a Contaminated Metal Surface

Maya Berlin-Udi

All surfaces generate electric-field noise, yet the physical origins of this noise are not well understood. This has been an active area of research in the ion trapping community for the past two decades, as ions are highly sensitive to electric-field fluctuations. With our work, we aim to illuminate the microscopic processes that drive charge dynamics on metal surfaces, so as to enable the engineering of low noise quantum devices. We use single trapped calcium ions as detectors to study the 1/f noise generated by the surfaces of ion traps. We the study this noise by observing how it responds to changes in the properties of the trap surface. The surface properties are altered using treatments including prolonged heating, argon ion milling, and electron bombardment. In situ characterization tools are used to monitor the effects of these treatments. Our measurements are consistent with noise produced by an ensemble of thermally activated fluctuators, so our data is discussed in this context. In this dissertation, we present results from a lengthy series of surface treatment experiments, the majority of which took place on a single aluminum-copper substrate. The results of these experiments indicate that argon ion milling can lower noise both by removing contaminants and by altering the morphology of the trap surface. The effects of morphology are isolated from the effects of contaminant removal via heat treatments, which alter the structure of the surface without changing its chemical composition. Through electron bombardment experiments, we begin an exploration of the relationship between hydrocarbon adsorbate structure and electric-field noise. In addition, we compare the noise characteristics of a set of similarly fabricated traps, and determine that atmosphere exposure has a major impact on noise produced by aluminum-copper films.These experiments establish links between the electric-field noise characteristics and the microscopic properties of a contaminated metal trap surface. The insights we draw in this work can inform the next generation of ion trap engineering, storage, and treatment.

•Jan 1, 2020•1 citation

Probing Electric Field Noise Above Ion Traps from 7–600 K and the Influence of Surface Structure on Noise Levels

Benjamin Saarel

Electric field noise produced by the surface of ion trap electrodes reduces the fidelity of quantum computing operations. Despite decades of investigation its microscopic origins remain unclear.This thesis investigates the origins of surface electric field noise by examining its dependence on trap temperature. A set of Al-Cu surface Paul traps are fabricated together and sent to MIT Lincoln Labs (MITLL) and the University of California, Berkeley (UCB). MITLL measures noise from 7 K to room temperature above a first trap and UCB measures noise from room temperature to 590 K above a second trap. The noise measurements from the two experiments are combined to study the noise dependence over the full temperature range from 7-590 K. This is the largest temperature range ever studied using a single trap design and connects the temperature ranges used in all previous studies.We find qualitatively different behaviors at low and high temperatures: from 7-430 K we find that the noise follows the same power-law scaling reported in previous cryogenic studies. At temperatures from 430-590 K, we find that the noise increases much more rapidly than predicted by the power-law scaling. We note a particularly sharp rise in noise at 560 K, which is similar to the sharp rise in noise reported in a previous high-temperature study of a different Al-Cu trap. To determine which physical processes are associated with the change in noise at elevated trap temperatures, we investigate how the material state of the trap electrodes changes when they are heated. We find that the primary physical process associated with the change in noise at high temperature is thermally-activated atom diffusion within the films.This thesis also investigates if the surface structure of room-temperature Au ion traps affects noise levels. We use a heat treatment to restructure the surface of the traps and measure the resulting change in noise. We find that the heat treatment leads to significant changes to the surface structure but causes only a modest change to noise levels. This indicates that the heat-induced changes to the surface do not strongly affect noise. We also note that the noise magnitude observed above these Au traps is state-of-the-art for room-temperature, untreated surface ion traps. This noise level can be explained by modeling the contamination that exists on the trap surface as a dielectric with a loss tangent of tan θ ≈ 0.01.Finally, this thesis investigates the origin of elevated noise levels in one region of a Au surface ion trap. We find that micron-sized particles are located where noise levels are highest, indicating that these particles are likely responsible for the noise. We can explain the magnitude, frequency, and distance dependence of the noise if we treat the particles as a lossy dielectric with a loss tangent tan θ ≈ 0.3.

•May 1, 2026•0 citations

Influence of monolayer contamination on electric-field-noise heating in ion traps

Arghavan Safavi-Naini, E. Kim, Philippe F. Weck +2 more

Electric field noise is a hinderance to the assembly of large-scale quantum computers based on entangled trapped ions. Apart from ubiquitous technical noise, experimental studies of trapped ion heating have revealed additional limiting contributions to this noise, originating from atomic processes on the electrode surfaces. In a recent work [Safavi-Naini, Rabl, Weck, and Sadeghpour, Phys. Rev. A 84, 023412 (2011)] we described a microscopic model for this excess electric field noise, which points a way towards a more systematic understanding of surface adsorbates as progenitors of electric field jitter noise. Here, we address the impact of surface monolayer contamination on adsorbate-induced noise processes. Using exact numerical calculations for H and N atomic monolayers on a Au(111) surface, representing opposite extremes of physisorption and chemisorption, we show that an additional monolayer can significantly affect the noise power spectrum and, respectively, enhance and suppress the heating rates.

arXiv:1210.0044•Physical Review A•Feb 22, 2013•33 citations

Measurements of electric field noise and light-inducedcharging in cryogenic surface electrode ion traps; Measurements of electric field noise and light-inducedcharging in Al and Cu surface electrode ion traps at cryogenictemperatures

Nathan S. Lachenmyer

Ion traps provide an excellent tool for controlling and observing the state of a single trapped ion. For this reason, ion traps have been proposed as a possible system for large-scale quantum computation. However, many obstacles must be overcome before quantum computing can become a reality. In particular, perturbations in the electric field due to noise and electrode charging must be reduced to increase coherence of the motional quantum state. Gold has been a popular choice in the past due to its inert properties; however, it is undesirable due its incompatibility with CMOS technology. This has led to increased research into alternative CMOS-compatible materials, such as aluminum and copper. This thesis presents measurements of electric field noise and light-induced charging in aluminum, copper, and gold surface electrode traps. In addition, the effect of oxide growth on field noise and electrode charging is explored by controlling the thickness of aluminum oxide on several aluminum traps. The measurements show that electric field noise can be suppressed in aluminum traps to approximately 10-18 V2 cm-2 Hz-1, matching the noise exhibited in gold traps, and that copper traps exhibit noise within an order of magnitude of that in aluminum and gold. However, the natural oxide of aluminum poses many problems towards high-performance aluminum ion traps. The electric field noise is shown to be strongly dependent on the oxide thickness, increasing the noise by a factor of about 10 until saturation at a thickness of 13 nm. Charging of surface electrodes is shown to be highly dependent upon the material, but the model presented does not match the experimental data and is found to be incomplete. These results indicate that ion traps made out of CMOS-compatible materials can perform as well as more traditional traps fabricated from gold with respect to heating and charging as long as methods are developed for controlling oxide growth.

•Jan 1, 2010•0 citations

Surface noise analysis using a single-ion sensor

Nikos Daniilidis, S. Gerber, G. Bolloten +5 more

We use a single-ion electric-field noise sensor in combination with in situ surface treatment and analysis tools, to investigate the relationship between electric-field noise from metal surfaces in vacuum and the composition of the surface. These experiments are performed in a setup that integrates ion trapping capabilities with surface analysis tools. We find that treatment of an aluminum-copper surface with energetic argon ions significantly reduces the level of room-temperature electric-field noise, but the surface does not need to be atomically clean to show noise levels comparable to those of the best cryogenic traps. The noise levels after treatment are low enough to allow fault-tolerant trapped-ion quantum information processing on a microfabricated surface trap at room temperature.

Physical Review B•Jun 20, 2014•68 citations

100-Fold Reduction of Electric-Field Noise in an Ion Trap Cleaned with In Situ Argon-Ion-Beam Bombardment

Dustin A. Hite, Yves Colombe, A. C. Wilson +8 more

Motional heating of trapped atomic ions is a major obstacle to their use as quantum bits in a scalable quantum computer. The detailed physical origin of this heating is not well understood, but experimental evidence suggests that it is caused by electric-field noise emanating from the surface of the trap electrodes. In this study, we have investigated the role of adsorbates on the electrodes by identifying contaminant overlayers, implementing an in situ argon-ion-beam cleaning treatment, and measuring ion heating rates before and after treating the trap electrodes' surfaces. We find a 100-fold reduction in heating rate after treatment. The experiments described here are sensitive to low levels of electric-field noise in the MHz frequency range. Therefore, this approach could become a useful tool in surface science that complements established techniques.

arXiv:1112.5419•Physical Review Letters•Sep 4, 2012•175 citations
FOURIER TRANSFORM INFRARED ANALYSIS OF SURFACE ION TRAPS Abstract: This study examines gold and copper-aluminum surfaces in air and vacuum via Fourier-transform in- frared spectroscopy to learn more about the causes of electric surface noise in ion traps. The FTIR spectra show traces contamination, including unique fingerprints in the range of 4000 to 600 cm-1. We study how the spec- tra change when the surfaces are exposed to controlled hydrocarbon contamination. We also study wheth- er procedures commonly used in ion trapping such baking for establishing ultra-high vacuum, and exposure to blue to ultraviolet light radiation alter the surface. Spectra of individual surfaces are found to differ more from each other than they do under these procedures. This work is based off of the first author’s honors thesis. BY WILLIAM TOKUMARU, ISHAN TALUKDAR, & HARTMUT HAEFFNER LAYOUT BY ELLIS VAVRA, REBECCA CHAN, AVANI VAID, HYEONJI SHIM, HARRISON RAMSAY INTRODUCTION AND BACKGROUND Quantum computing has exciting applications ranging from clever solutions for optimization problems to superior im- plementations of existing algorithms. [1] It should enable cracking of traditional cryptography, while likewise protecting infor- mation. One of the most promising ways to create a universal quantum computer is using trapped ions. [1] While quantum computing with trapped ions is well advanced, surface noise prevents progress towards smaller and more compact systems which would allow for faster and more flexible quantum computing architectures. [2, 3] Ion “qubits” are controlled by manipulating electronic and motional states of ions with lasers. Unfortunately, electric field noise limits the coherence of multi-qubit operations by destroying the quan- tum information in the quantum bus connecting the respective qubits. [2] After eliminating technical noise, the remaining noise is too large to be explained by Johnson noise and unlikely to be a systematic or a measurement error. Instead, the noise has been reduced by cooling the electrodes to cryogenic temperatures, by increasing the distance of the ions from the surfaces, and by surface treatment with energetic Argon ions. Concentrated laser radiation has been reported to both decrease and increase heat- ing rates. [4-10] In particular, surface treatment experiments suggest that surface contaminants play an important role in the observed noise. [6] Indeed, Auger electron spectroscopy shows that carbon and oxygen are present before treatment and are removed by the energetic Argon ions. [7, 8] However, the experiments in Ref. [8] also report that subsequent re-contamination from molecules present in Ultra-High Vacuum (UHV) does not let the noise reappear. Carbon contamination may be either in the form of atomic carbon or of hydrocarbons deposited on the electrodes somewhere during the fabrication, assembly or baking proce- dures. The studies in this paper aim at comprehending the noise mechanisms to help in future experimental planning. They also apply to numerous other fields studying electric noise near surfaces, including engineering nanoelectronics and supercon- ducting electronics, detection of Casimir forces in quantum field theory, tests of general relativity, and hybrid quantum devices. Organic materials present in air tend to adsorb onto metal and form nanostructures to reduce the free energy be- tween surfaces and the environment. [16] A common model for these contaminants is based around Self-assembled Monolayers (SAMs). [17] These molecular structures are formed from exposure to fluids and gases with organic content and organize sponta- neously into crystalline-like adatom structures. They commonly appear on gold and copper surfaces, both of which are common traps electrode materials. [18-27] Many SAMs are “alkanethiols,” FALL 2016 | Berkeley Scientific Journal
All surfaces generate electric-field noise, yet the physical origins of this noise are not well understood. This has been an active area of research in the ion trapping community for the past two decades, as ions are highly sensitive to electric-field fluctuations. With our work, we aim to illuminate the microscopic processes that drive charge dynamics on metal surfaces, so as to enable the engineering of low noise quantum devices. We use single trapped calcium ions as detectors to study the 1/f noise generated by the surfaces of ion traps. We the study this noise by observing how it responds to changes in the properties of the trap surface. The surface properties are altered using treatments including prolonged heating, argon ion milling, and electron bombardment. In situ characterization tools are used to monitor the effects of these treatments. Our measurements are consistent with noise produced by an ensemble of thermally activated fluctuators, so our data is discussed in this context. In this dissertation, we present results from a lengthy series of surface treatment experiments, the majority of which took place on a single aluminum-copper substrate. The results of these experiments indicate that argon ion milling can lower noise both by removing contaminants and by altering the morphology of the trap surface. The effects of morphology are isolated from the effects of contaminant removal via heat treatments, which alter the structure of the surface without changing its chemical composition. Through electron bombardment experiments, we begin an exploration of the relationship between hydrocarbon adsorbate structure and electric-field noise. In addition, we compare the noise characteristics of a set of similarly fabricated traps, and determine that atmosphere exposure has a major impact on noise produced by aluminum-copper films.These experiments establish links between the electric-field noise characteristics and the microscopic properties of a contaminated metal trap surface. The insights we draw in this work can inform the next generation of ion trap engineering, storage, and treatment.
Electric field noise produced by the surface of ion trap electrodes reduces the fidelity of quantum computing operations. Despite decades of investigation its microscopic origins remain unclear.This thesis investigates the origins of surface electric field noise by examining its dependence on trap temperature. A set of Al-Cu surface Paul traps are fabricated together and sent to MIT Lincoln Labs (MITLL) and the University of California, Berkeley (UCB). MITLL measures noise from 7 K to room temperature above a first trap and UCB measures noise from room temperature to 590 K above a second trap. The noise measurements from the two experiments are combined to study the noise dependence over the full temperature range from 7-590 K. This is the largest temperature range ever studied using a single trap design and connects the temperature ranges used in all previous studies.We find qualitatively different behaviors at low and high temperatures: from 7-430 K we find that the noise follows the same power-law scaling reported in previous cryogenic studies. At temperatures from 430-590 K, we find that the noise increases much more rapidly than predicted by the power-law scaling. We note a particularly sharp rise in noise at 560 K, which is similar to the sharp rise in noise reported in a previous high-temperature study of a different Al-Cu trap. To determine which physical processes are associated with the change in noise at elevated trap temperatures, we investigate how the material state of the trap electrodes changes when they are heated. We find that the primary physical process associated with the change in noise at high temperature is thermally-activated atom diffusion within the films.This thesis also investigates if the surface structure of room-temperature Au ion traps affects noise levels. We use a heat treatment to restructure the surface of the traps and measure the resulting change in noise. We find that the heat treatment leads to significant changes to the surface structure but causes only a modest change to noise levels. This indicates that the heat-induced changes to the surface do not strongly affect noise. We also note that the noise magnitude observed above these Au traps is state-of-the-art for room-temperature, untreated surface ion traps. This noise level can be explained by modeling the contamination that exists on the trap surface as a dielectric with a loss tangent of tan θ ≈ 0.01.Finally, this thesis investigates the origin of elevated noise levels in one region of a Au surface ion trap. We find that micron-sized particles are located where noise levels are highest, indicating that these particles are likely responsible for the noise. We can explain the magnitude, frequency, and distance dependence of the noise if we treat the particles as a lossy dielectric with a loss tangent tan θ ≈ 0.3.
Electric field noise is a hinderance to the assembly of large-scale quantum computers based on entangled trapped ions. Apart from ubiquitous technical noise, experimental studies of trapped ion heating have revealed additional limiting contributions to this noise, originating from atomic processes on the electrode surfaces. In a recent work [Safavi-Naini, Rabl, Weck, and Sadeghpour, Phys. Rev. A 84, 023412 (2011)] we described a microscopic model for this excess electric field noise, which points a way towards a more systematic understanding of surface adsorbates as progenitors of electric field jitter noise. Here, we address the impact of surface monolayer contamination on adsorbate-induced noise processes. Using exact numerical calculations for H and N atomic monolayers on a Au(111) surface, representing opposite extremes of physisorption and chemisorption, we show that an additional monolayer can significantly affect the noise power spectrum and, respectively, enhance and suppress the heating rates.
Ion traps provide an excellent tool for controlling and observing the state of a single trapped ion. For this reason, ion traps have been proposed as a possible system for large-scale quantum computation. However, many obstacles must be overcome before quantum computing can become a reality. In particular, perturbations in the electric field due to noise and electrode charging must be reduced to increase coherence of the motional quantum state. Gold has been a popular choice in the past due to its inert properties; however, it is undesirable due its incompatibility with CMOS technology. This has led to increased research into alternative CMOS-compatible materials, such as aluminum and copper. This thesis presents measurements of electric field noise and light-induced charging in aluminum, copper, and gold surface electrode traps. In addition, the effect of oxide growth on field noise and electrode charging is explored by controlling the thickness of aluminum oxide on several aluminum traps. The measurements show that electric field noise can be suppressed in aluminum traps to approximately 10-18 V2 cm-2 Hz-1, matching the noise exhibited in gold traps, and that copper traps exhibit noise within an order of magnitude of that in aluminum and gold. However, the natural oxide of aluminum poses many problems towards high-performance aluminum ion traps. The electric field noise is shown to be strongly dependent on the oxide thickness, increasing the noise by a factor of about 10 until saturation at a thickness of 13 nm. Charging of surface electrodes is shown to be highly dependent upon the material, but the model presented does not match the experimental data and is found to be incomplete. These results indicate that ion traps made out of CMOS-compatible materials can perform as well as more traditional traps fabricated from gold with respect to heating and charging as long as methods are developed for controlling oxide growth.
We use a single-ion electric-field noise sensor in combination with in situ surface treatment and analysis tools, to investigate the relationship between electric-field noise from metal surfaces in vacuum and the composition of the surface. These experiments are performed in a setup that integrates ion trapping capabilities with surface analysis tools. We find that treatment of an aluminum-copper surface with energetic argon ions significantly reduces the level of room-temperature electric-field noise, but the surface does not need to be atomically clean to show noise levels comparable to those of the best cryogenic traps. The noise levels after treatment are low enough to allow fault-tolerant trapped-ion quantum information processing on a microfabricated surface trap at room temperature.
Motional heating of trapped atomic ions is a major obstacle to their use as quantum bits in a scalable quantum computer. The detailed physical origin of this heating is not well understood, but experimental evidence suggests that it is caused by electric-field noise emanating from the surface of the trap electrodes. In this study, we have investigated the role of adsorbates on the electrodes by identifying contaminant overlayers, implementing an in situ argon-ion-beam cleaning treatment, and measuring ion heating rates before and after treating the trap electrodes' surfaces. We find a 100-fold reduction in heating rate after treatment. The experiments described here are sensitive to low levels of electric-field noise in the MHz frequency range. Therefore, this approach could become a useful tool in surface science that complements established techniques.