scholarly journals Effects of surface treatments on flux tunable transmon qubits

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
M. Mergenthaler ◽  
C. Müller ◽  
M. Ganzhorn ◽  
S. Paredes ◽  
P. Müller ◽  
...  
Keyword(s):  
Fault Tolerant ◽  
Ion Irradiation ◽  
Uv Light ◽  
Light Exposure ◽  
High Vacuum ◽  
Ion Bombardment ◽  
Ultra High Vacuum ◽  
Sweet Spot ◽  
Noise Sources ◽  
The Impact

AbstractOne of the main limitations in state-of-the art solid-state quantum processors is qubit decoherence and relaxation due to noise from adsorbates on surfaces, impurities at interfaces, and material defects. For the field to advance towards full fault-tolerant quantum computing, a better understanding of these microscopic noise sources is therefore needed. Here, we use an ultra-high vacuum package to study the impact of vacuum loading, UV-light exposure, and ion irradiation treatments on relaxation and coherence times, as well as slow parameter fluctuations of flux tunable superconducting transmon qubits. The treatments studied do not significantly impact the relaxation rate Γ1 and the echo decay rate $${{{\Gamma }}}_{2,{{{\rm{SS}}}}}^{{{{\rm{e}}}}}$$ Γ 2 , SS e at the sweet spot, except for Ne ion bombardment which reduces Γ1. In contrast, flux noise parameters are improved by removing magnetic adsorbates from the chip surfaces with UV-light and NH3 treatments. Additionally, we demonstrate that SF6 ion bombardment can be used to adjust qubit frequencies in situ and post-fabrication without affecting qubit relaxation and coherence times at the sweet spot.

Ar Cluster Ion Bombardment Effects on Semiconductor Surfaces

2000 ◽  
Vol 647 ◽  
Author(s):  
Toshio Seki ◽  
Kazumichi Tsumura ◽  
Takaaki Aoki ◽  
Jiro Matsuo ◽  
Gikan H. Takaoka ◽  
...  
Keyword(s):  
Surface Modification ◽  
Variable Temperature ◽  
Ion Beam ◽  
High Vacuum ◽  
Ion Bombardment ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Cluster Ion ◽  
Ion Impact ◽  
The Impact

AbstractNew surface modification processes have been demonstrated using gas cluster ion irradiations because of their unique interaction between cluster ions and surface atoms. For example, high quality ITO films could be obtained by O2 cluster ion assisted deposition at room temperature. It is necessary to understand the role of cluster ion bombardment during film formation for the further developments of this technology. Variable Temperature Scanning Tunneling Microscope (VT-STM) in Ultra High Vacuum (UHV) allows us to study ion bombardment effects on surfaces and nucleation growth at various temperatures.The irradiation effects between Ar cluster ion and Xe monomer ion were compared. When a Si(111) surface with Ge deposited to a few Å was annealed to 400°C, it was observed that many islands of Ge were formed. The surface with the Ge islands was irradiated by these ions. In the STM image of cluster-irradiated surface, large craters with diameter of about 100 Å were observed, while only small traces with diameter of about 20 Å were observed in monomer-irradiated surface. The number of Ge atoms displaced by one Ar cluster ion impact was much larger than that by one Xe ion impact. This result indicates that Ar cluster ion impacts can enhance the physical modification of Ge islands. When the sample irradiated with Ar cluster was annealed at 600°C, the hole remained, but the outer rim of the crater disappeared and the surface structure was reconstructed at the site of the rim. The depth of damage region in the target became shallower with decrease of the impact energy. These results indicate that low damage and useful surface modification can be realized using the cluster ion beam.

scholarly journals Contribution of Different Noise Sources to the Relative Instability of Laser Systems Stabilized by External Silicon Cavities

Vestnik RFFI ◽  
2019 ◽  
Author(s):  
Denis S . Kryuchkov ◽  
Gulnara A. Vishnyakova ◽  
Ksenia Yu. Khabarova ◽  
Konstantin S. Kudeyarov ◽  
Nikita O. Zhadnov ◽  
...  
Keyword(s):  
Crystalline Silicon ◽  
High Vacuum ◽  
Frequency Instability ◽  
Ultra High Vacuum ◽  
Signal Frequency ◽  
Noise Sources ◽  
Fabry Perot ◽  
Laser Systems ◽  
Stable Laser ◽  
Frequency Counting

Here we consider creation of laser systems stabilized by external macroscopic monolithic Fabry – Perot cavities made of single-crystalline silicon operating at cryogenic temperatures. Fundamental thermal noise floor for fractional frequency instability was evaluated with its dependency on cavity’s spacer, mirror’s substrate and coatings material. Silicon cavities with dielectric SiO2 /Ta2 O5 and crystalline GaAs/InGaAs mirror coatings were created, its finesse at room temperatures was investigated. Two ultra-high vacuum optical cryostats were developed. Two ultra-stable laser systems based on cavities with dielectric mirrors were assembled. Comparison scheme via beat signal frequency counting was implemented for the characterization purpose. Different noise sources presenting at assembled systems are considered. Its impact to relative frequency instability of our laser systems is being explored.

scholarly journals Laboratory Simulations of Physico-chemical Processes under Interstellar Conditions

2012 ◽  
Vol 10 (H16) ◽  
pp. 713-714
Author(s):  
Guillermo M. Muñoz Caro
Keyword(s):  
Ion Irradiation ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Photon Flux ◽  
X Rays ◽  
Dust Grains ◽  
Dark Cloud ◽  
Interstellar Clouds ◽  
Laboratory Simulations ◽  
Gas Molecules

AbstractThe accretion and desorption of gas molecules on cold dust grains play an important role in the evolution of dense clouds and circumstellar regions around YSOs. Some of the gas molecules detected in interstellar clouds were likely synthesized in icy dust grains and ejected to the gas. But in dark cloud interiors, with temperatures as low as 10–20 K, thermal desorption is negligible and a non-thermal mechanism like ice photodesorption is required. Reactions in the ice matrix are driven by energetic processing such as photon and ion irradiation. In circumstellar regions the photon flux (UV and X-rays) is expected to be significantly higher than in dense cloud interiors, icy grain mantles present in the outer parts will experience significant irradiation. The produced radicals lead to the formation of new species in the ice, some of them of prebiotic interest. Laboratory simulations of these processes are required for their understanding. The new ultra-high vacuum set-ups introduce some important improvements.

scholarly journals Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase

2018 ◽  
Vol 612 ◽  
pp. A88 ◽  
Author(s):  
N. F. W. Ligterink ◽  
C. Walsh ◽  
R. G. Bhuin ◽  
S. Vissapragada ◽  
J. Terwisscha van Scheltinga ◽  
...  
Keyword(s):  
Gas Phase ◽  
Thermal Desorption ◽  
High Vacuum ◽  
Protoplanetary Disk ◽  
Ultra High Vacuum ◽  
Indirect Pathway ◽  
Cold Environments ◽  
Chemical Modelling ◽  
Phase Chemistry ◽  
The Impact

Context. Methanol is formed via surface reactions on icy dust grains. Methanol is also detected in the gas-phase at temperatures below its thermal desorption temperature and at levels higher than can be explained by pure gas-phase chemistry. The process that controls the transition from solid state to gas-phase methanol in cold environments is not understood. Aims. The goal of this work is to investigate whether thermal CO desorption provides an indirect pathway for methanol to co-desorb at low temperatures. Methods. Mixed CH3OH:CO/CH4 ices were heated under ultra-high vacuum conditions and ice contents are traced using RAIRS (reflection absorption IR spectroscopy), while desorbing species were detected mass spectrometrically. An updated gas-grain chemical network was used to test the impact of the results of these experiments. The physical model used is applicable for TW Hya, a protoplanetary disk in which cold gas-phase methanol has recently been detected. Results. Methanol release together with thermal CO desorption is found to be an ineffective process in the experiments, resulting in an upper limit of ≤ 7.3 × 10−7 CH3OH molecules per CO molecule over all ice mixtures considered. Chemical modelling based on the upper limits shows that co-desorption rates as low as 10−6 CH3OH molecules per CO molecule are high enough to release substantial amounts of methanol to the gas-phase at and around the location of the CO thermal desorption front in a protoplanetary disk. The impact of thermal co-desorption of CH3OH with CO as a grain-gas bridge mechanism is compared with that of UV induced photodesorption and chemisorption.

The Scanning Photoelectron Microscope : A Novel Tool in Surface Science

1990 ◽  
Vol 48 (1) ◽  
pp. 556-557
Author(s):  
A. von Oertzen ◽  
H.H. Rotermund ◽  
S. Jakubith ◽  
S. Kubala ◽  
G. Ertl
Keyword(s):  
Surface Science ◽  
Uv Light ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Optics ◽  
Experimental Setup ◽  
Photoelectron Emission ◽  
Small Aperture ◽  
New Approach ◽  
Work Functions

Photoelectron microscopes using electron optics had been built long before. Until recently these microscopes were not widely used in surface science due to unsufficient vacuum conditions as well as weak image intensifying devices. In this paper we will present a new approach to photoelectron microscopy, the Scanning Photoelectron Microscope (SPM).Photoelectron emission will occur as soon as the photon energy is higher than the work function on the illuminated area. Since work functions never exceed 6.5 eV, ultraviolet (UV) light with λ ≥ 190 nm will be appropriate. This kind of radiation is a very gentle probe, even for sensitive adlayers.The experimental setup is shown schematicaly in Fig. 1. A UV light optics outside the ultra high vacuum (UHV) system focusses the actual 30 W Deuterium discharge lamp through a grid monochromator onto a small aperture (50 to 400 microns). The aperture hole is projected with a reflecting microscope objective (Schwarzschild type) onto the surface of the sample yielding a lateral resolution of about 3 microns.

Advances in Photoelectron Imaging

1990 ◽  
Vol 48 (1) ◽  
pp. 218-219
Author(s):  
O. Hayes Griffith ◽  
G. Bruce Birrell ◽  
Douglas H. Habliston ◽  
Karen K. Hedberg
Keyword(s):  
Electron Microscopy ◽  
Uv Light ◽  
High Vacuum ◽  
Photoelectric Effect ◽  
Ultra High Vacuum ◽  
Photoelectron Imaging ◽  
Vacuum Technology ◽  
The Common ◽  
Optical Analog ◽  
Source Of Information

There are many possible strategies of photoelectron imaging. The common theme is to form the image with electrons that have been photoejected from a surface by UV light (i.e. the photoelectric effect). Currently the highest resolution method is photoelectron microscopy (PEM), which is also called photoemission electron microscopy (PEEM). This approach has its roots in the early developments in electron microscopy in Germany. However, modern ultra high vacuum technology and image enhancement techniques have made possible significant advances in the capabilities of photoelectron imaging.Photoelectron microscopy is the electron optical analog of fluorescence microscopy. Light is focused on a specimen and the emitted electrons are accelerated, and the image magnified by means of an electron optical system. The main advantage of photoelectron microscopy is the source of contrast. Small differences in the bonding of outermost electrons can cause significant contrast between molecules that would be otherwise difficult to detect. Biological systems are rich in macromolecules that differ in molecular ionization potentials and this source of information remains largely unexplored.

Adhesion Enhancement Produced by MEV Ions

1992 ◽  
Vol 268 ◽  
Author(s):  
Stephen Sugden ◽  
Carl J. Sofield ◽  
Martin P. Murrell
Keyword(s):  
Ion Irradiation ◽  
High Vacuum ◽  
Gain Control ◽  
Heavy Ion ◽  
Ultra High Vacuum ◽  
Radiation Processing ◽  
Surface And Interface ◽  
Film Adhesion ◽  
Thin Film Adhesion ◽  
Ionising Radiations

ABSTRACTIonising radiations have been observed to produce significant improvements in thin film adhesion by several experimental groups. We present the results of an exhaustive and conclusive series of experiments on the effect of clean processing and heavy ion irradiation on the adhesion of metal films to substrates of silicon and tantalum. The experiments were performed in a unique research-scale Ultra High Vacuum Cluster tool, to gain control of the all important surface and interface compositions.Our results show that adhesion is greatest for films deposited on atomically clean surfaces. Such films adhere better than conventionally deposited films subjected to a post deposition irradiation treatment. Clean processed samples show no benefit from subsequent radiation processing. Our results are consistent with the radiation enhanced adhesion phenomenon being due to the radiolysis of interfacial contaminant layers, producing an interface with lower interfacial energy and hence better bonding. Where adhesion enhancement is observed, the process is consistent with a semi-empirical model of the process using an activation energy of some 5 eV per atom.

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